This document provides guidance for selecting concrete materials for civil works structures. It establishes standard practices for investigating and selecting cementitious materials like Portland cement, blended cements, pozzolans, and slag. It also provides guidance for selecting aggregates, mixing water, chemical admixtures, and investigating available material sources. The document contains policies, requirements, and considerations for choosing appropriate materials based on the type of structure and project requirements. It seeks to ensure high quality, durable concrete is used in civil works projects.

1. CECW-EG
Engineer
Manual
1110-2-2000
Department of the Army
U.S. Army Corps of Engineers
Washington, DC 20314-1000
EM 1110-2-2000
1 February 1994
Engineering and Design
STANDARD PRACTICE FOR CONCRETE
FOR CIVIL WORKS STRUCTURES
Distribution Restriction Statement
Approved for public release; distribution is
unlimited.

2. EM 1110-2-2000
3 February 1994
US Army Corps
of Engineers
ENGINEERING AND DESIGN
Standard Practice for Concrete
for Civil Works Structures
ENGINEER MANUAL

3. CECW-EI
Manual
No, 111o-2-2000
DEPARTMENT OF THE ARMY
U.S. Army Corps of Engineers
Washington, DC 20314-1000
EM 111 o-2-2000
Change 2
31 March 01
Engineering and Design
STANDARD PRACTICE FOR CONCRETE
FOR CIVIL WORKS STRUCTURES
1. This Change 2 to EM 1110-2-2000, 1 February 1994, provides updated guidance for the
selection of aggregates in Chapter 2.
2. Substitute the attached pages as shown below:
Remove Page Insert page
2-10 2-10
2-11 2-11
3. File this change sheet in front of the publication for reference purposes.
FOR THE COMMANDER:
Colonel, Corps of Engineers
Chief of Staff

4. DEPARTMENT OF THE ARMY EM 1110-2-2000
U.S. Army Corps of Engineers Change 1
CECW-ED Washington, DC 20314-1000
Manual
No. 1110-2-2000 31 July 94
Engineering and Design
STANDARD PRACTICE FOR CONCRETE
FOR CIVIL WORKS STRUCTURES
1. This Change 1 to EM 1110-2-2000, 1 February 1994, updates Chapter 2.
2. Substitute the attached pages as shown below:
Remove page Insert page
2-1 2-1
2-6 2-6
3. File this change sheet in front of the publication for reference purposes.
FOR THE COMMANDER:
WILLIAM D. BROWN
Colonel, Corps of Engineers
Chief of Staff

5. DEPARTMENTDEPARTMENT OFOF THETHE ARMYARMY EM 1110-2-2000
US Army Corps of Engineers
CECW-EG Washington, DC 20314-1000
Manual
No. 1110-2-2000 1 February 1994
Engineering and Design
STANDARD PRACTICE FOR CONCRETE
FOR CIVIL WORKS STRUCTURES
1. Purpose. The purpose of this manual is to provide information and guidance for the investigation and
selection of concrete materials for civil works concrete structures. Elements discussed include design studies and
reports, preparation of contract plans and specifications, construction preparation, and concrete construction quality
verification. Emphasis is placed on the problems of concrete for hydraulic structures. Roller-compacted concrete,
shotcrete, rigid pavement, architectural concrete, and concrete for repairs are not included. These subjects are
discussed in EM 1110-2-2006, Roller-Compacted Concrete; EM 1110-2-2005, Standard Practice for Shotcrete; TM
5-822-7, Standard Practice for Concrete Pavements; EM 1110-1-2009, Architectural Concrete; and EM 1110-2-
2002, Evaluation and Repair of Concrete Structures, respectively.
2. Applicability. This manual is applicable to all HQUSACE elements, major subordinate commands, districts,
laboratories, and field operating activities having civil works responsibilities.
FOR THE COMMANDER:
WILLIAM D. BROWN
Colonel, Corps of Engineers
Chief of Staff
This manual supersedes EM 1110-2-2000, 5 September 1985.

6. DEPARTMENT OF THE ARMY EM 1110-2-2000
US Army Corps of Engineers
CECW-EG Washington, DC 20314-1000
Manual
No. 1110-2-2000 1 February 1994
Engineering and Design
STANDARD PRACTICE FOR CONCRETE
FOR CIVIL WORKS STRUCTURES
Table of Contents
Subject Paragraph Page Subject Paragraph Page
Chapter 1
Introduction and Policy
Purpose . . . . . . . . . . . . . . . . . . . . . . 1-1 1-1
Applicability . . . . . . . . . . . . . . . . . . 1-2 1-1
References . . . . . . . . . . . . . . . . . . . 1-3 1-1
Explanation of Abbreviations . . . . . . . 1-4 1-1
Engineering Responsibilities
and Requirements . . . . . . . . . . . . . . 1-5 1-1
Reconnaissance phase . . . . . . . . . . 1-5a 1-1
Feasibility phase . . . . . . . . . . . . . . 1-5b 1-1
Preconstruction engineering and
design phase . . . . . . . . . . . . . . . 1-5c 1-1
Construction phase . . . . . . . . . . . . 1-5d 1-1
Delays in Contract Awards . . . . . . . . . 1-6 1-2
Chapter 2
Investigation and Selection of Materials
Introduction . . . . . . . . . . . . . . . . . . . 2-1 2-1
Cementitious Materials . . . . . . . . . . . 2-2 2-1
General . . . . . . . . . . . . . . . . . . . . 2-2a 2-1
Types . . . . . . . . . . . . . . . . . . . . . 2-2b 2-1
Portland cement . . . . . . . . . . . . 2-2b(1) 2-1
Blended hydraulic cement . . . . . 2-2b(2) 2-1
Pozzolan . . . . . . . . . . . . . . . . . 2-2b(3) 2-1
GGBF slag . . . . . . . . . . . . . . . 2-2b(4) 2-1
Other hydraulic cements . . . . . . 2-2b(5) 2-1
Silica fume . . . . . . . . . . . . . . . 2-2b(6) 2-1
Air-entraining portland cement . . 2-2b(7) 2-1
Selection of cementitious materials . 2-2c 2-1
General . . . . . . . . . . . . . . . . . . 2-2c(1) 2-1
Type of structure . . . . . . . . . . . 2-2c(2) 2-1
Other requirements . . . . . . . . . . 2-2c(3) 2-2
Requirements for use of other
hydraulic cements . . . . . . . . . . 2-2c(4) 2-4
Pozzolans . . . . . . . . . . . . . . . . 2-2c(5) 2-4
Availability investigation of
cementitious materials . . . . . . . . 2-2d 2-5
General . . . . . . . . . . . . . . . . . . 2-2d(1) 2-5
Portland cement and blended
hydraulic cements . . . . . . . . . . 2-2d(2) 2-5
Pozzolans . . . . . . . . . . . . . . . . 2-2d(3) 2-6
GGBF slag . . . . . . . . . . . . . . . 2-2d(4) 2-6
Silica fume . . . . . . . . . . . . . . . 2-2d(5) 2-6
Aggregates . . . . . . . . . . . . . . . . . . . 2-3 2-6
General . . . . . . . . . . . . . . . . . . . . 2-3a 2-6
Sources of aggregate
(Government or commercial) . . 2-3a(1) 2-6
Minor structures . . . . . . . . . . . . 2-3a(2) 2-7
Availability investigation . . . . . . . . 2-3b 2-7
General . . . . . . . . . . . . . . . . . . 2-3b(1) 2-7
Service records . . . . . . . . . . . . . 2-3b(2) 2-7
Field exploration and sampling
of undeveloped sources . . . . . . 2-3b(3) 2-7
Field exploration and sampling
of developed sources . . . . . . . 2-3b(4) 2-7
Testing potential aggregate
sources . . . . . . . . . . . . . . . . . 2-3b(5) 2-8
Evaluating aggregate qualities . . 2-3b(6) 2-8
Nominal maximum size
aggregate . . . . . . . . . . . . . . . . 2-3b(7) 2-12
Fine aggregate grading
requirements . . . . . . . . . . . . . 2-3b(8) 2-12
Required tests and test limits . . . 2-3b(9) 2-13
Aggregate processing study . . . . 2-3b(10) 2-13
Location of government-furnished
quarry or pit . . . . . . . . . . . . . 2-3b(11) 2-13
Water for Mixing and Curing . . . . . . . 2-4 2-14
General . . . . . . . . . . . . . . . . . . . . 2-4a 2-14
Mixing water . . . . . . . . . . . . . . . . 2-4b 2-14
Curing water . . . . . . . . . . . . . . . . 2-4c 2-14
Chemical Admixtures . . . . . . . . . . . . 2-5 2-14
General . . . . . . . . . . . . . . . . . . . . 2-5a 2-14
Air-entraining admixtures . . . . . . . 2-5b 2-14
Policy . . . . . . . . . . . . . . . . . . . 2-5b(1) 2-14
Strength loss . . . . . . . . . . . . . . 2-5b(2) 2-15
i

7. EM 1110-2-2000
1 Feb 94
Table of Contents (Continued)
Subject Paragraph Page Subject Paragraph Page
Bleeding . . . . . . . . . . . . . . . . . 2-5b(3) 2-15
Batching AEA . . . . . . . . . . . . . 2-5b(4) 2-15
Dosage . . . . . . . . . . . . . . . . . . 2-5b(5) 2-15
Effects of water content
on air content . . . . . . . . . . . . 2-5b(6) 2-15
Effects of fine aggregate grading
on air content . . . . . . . . . . . . 2-5b(7) 2-15
Effects of temperature on
air content . . . . . . . . . . . . . . . 2-5b(8) 2-15
Effect of other admixtures
on air content . . . . . . . . . . . . 2-5b(9) 2-15
Effect of mixing action on
air content . . . . . . . . . . . . . . . 2-5b(10) 2-15
Accelerating admixture . . . . . . . . . 2-5c 2-15
Uses . . . . . . . . . . . . . . . . . . . . 2-5c(1) 2-16
Nonchloride admixtures . . . . . . . 2-5c(2) 2-16
Effects on fresh concrete
properties . . . . . . . . . . . . . . . 2-5c(3) 2-16
Effect on hardened concrete
properties . . . . . . . . . . . . . . . 2-5c(4) 2-16
Other methods of accelerating
strength developments . . . . . . . 2-5c(5) 2-16
Retarding admixtures . . . . . . . . . . 2-5d 2-16
General uses . . . . . . . . . . . . . . 2-5d(1) 2-16
Dosage . . . . . . . . . . . . . . . . . . 2-5d(2) 2-16
Batching . . . . . . . . . . . . . . . . . 2-5d(3) 2-17
Effect on strength . . . . . . . . . . . 2-5d(4) 2-17
Water-reducing admixtures . . . . . . 2-5e 2-17
Use in mass concrete . . . . . . . . 2-5e(1) 2-17
Dosage . . . . . . . . . . . . . . . . . . 2-5e(2) 2-17
Use in hot or cool weather . . . . . 2-5e(3) 2-17
Air entrainment . . . . . . . . . . . . 2-5e(4) 2-17
Bleeding . . . . . . . . . . . . . . . . . 2-5e(5) 2-17
High-range water-reducing
admixtures (superplasticizers) . . . 2-5f 2-17
Effect on workability . . . . . . . . 2-5f(1) 2-18
Effect on segregation and
bleeding . . . . . . . . . . . . . . . . 2-5f(2) 2-18
Effect on air entrainment . . . . . . 2-5f(3) 2-18
Effect on setting time . . . . . . . . 2-5f(4) 2-18
Compatibility with other
admixtures . . . . . . . . . . . . . . . 2-5f(5) 2-18
Antiwashout admixtures . . . . . . . . 2-5g 2-18
General . . . . . . . . . . . . . . . . . . 2-5g(1) 2-19
Batching . . . . . . . . . . . . . . . . . 2-5g(2) 2-19
Air entrainment . . . . . . . . . . . . 2-5g(3) 2-19
Bleeding . . . . . . . . . . . . . . . . . 2-5g(4) 2-19
Retardation . . . . . . . . . . . . . . . 2-5g(5) 2-19
Compatibility . . . . . . . . . . . . . . 2-5g(6) 2-19
Dosage . . . . . . . . . . . . . . . . . . 2-5g(7) 2-19
Pumping . . . . . . . . . . . . . . . . . 2-5g(8) 2-19
Extended set-control admixtures . . . 2-5h 2-19
General . . . . . . . . . . . . . . . . . . 2-5h(1) 2-19
Stabilizer . . . . . . . . . . . . . . . . . 2-5h(2) 2-20
Activator . . . . . . . . . . . . . . . . . 2-5h(3) 2-20
Effect on hardened properties . . . 2-5h(4) 2-20
Dosage . . . . . . . . . . . . . . . . . . 2-5h(5) 2-20
Antifreeze admixtures . . . . . . . . . . 2-5i 2-20
Composition . . . . . . . . . . . . . . . 2-5i(1) 2-20
Batching . . . . . . . . . . . . . . . . . 2-5i(2) 2-21
Effect on strength . . . . . . . . . . . 2-5i(3) 2-21
Effect on resistance to freezing
and thawing . . . . . . . . . . . . . . . 2-5i(4) 2-21
Use with reactive aggregates . . . 2-5i(5) 2-21
Corrosion of steel . . . . . . . . . . . 2-5i(6) 2-21
Cost benefits . . . . . . . . . . . . . . 2-5i(7) 2-21
Chapter 3
Construction Requirements and
Special Studies
Construction Requirements . . . . . . . . 3-1 3-1
General . . . . . . . . . . . . . . . . . . . . 3-1a 3-1
Batch-plant location . . . . . . . . . . . 3-1b 3-1
Batch-plant type . . . . . . . . . . . . . . 3-1c 3-1
Mixer type . . . . . . . . . . . . . . . . . . 3-1d 3-1
Batching and mixing plant capacity 3-1e 3-2
Monolith size . . . . . . . . . . . . . . 3-1e(1) 3-2
Traditional placing method . . . . 3-1e(2) 3-2
Equation for minimum placing
capacity . . . . . . . . . . . . . . . . 3-1e(3) 3-2
Graphic calculation of minimum
placing capacity . . . . . . . . . . . 3-1e(4) 3-2
Other placing methods . . . . . . . 3-1e(5) 3-5
Conveying and placing
considerations . . . . . . . . . . . . . . 3-1f 3-5
Use of epoxy resins . . . . . . . . . . . 3-1g 3-5
Special Studies . . . . . . . . . . . . . . . . . 3-2 3-5
General . . . . . . . . . . . . . . . . . . . . 3-2a 3-5
Thermal studies . . . . . . . . . . . . . . 3-2b 3-5
Material properties needed for a
thermal study . . . . . . . . . . . . . 3-2b(1) 3-5
Time of completion of thermal
study . . . . . . . . . . . . . . . . . . 3-2b(2) 3-6
Temperature control techniques . 3-2b(3) 3-6
Numerical analysis of temperature
control techniques . . . . . . . . . 3-2b(4) 3-6
Abrasion-erosion studies . . . . . . . . 3-2c 3-6
General . . . . . . . . . . . . . . . . . . 3-2c(1) 3-6
ii

8. EM 1110-2-2000
1 Feb 94
Table of Contents (Continued)
Subject Paragraph Page Subject Paragraph Page
Test method . . . . . . . . . . . . . . . 3-2c(2) 3-6
Application of test results . . . . . 3-2c(3) 3-6
Mixer grinding studies . . . . . . . . . 3-2d 3-6
Concrete subjected to high velocity
flow of water . . . . . . . . . . . . . . . 3-2e 3-7
General . . . . . . . . . . . . . . . . . . 3-2e(1) 3-7
Quality of concrete . . . . . . . . . . 3-2e(2) 3-7
Construction joints . . . . . . . . . . 3-2e(3) 3-7
Unformed surfaces . . . . . . . . . . 3-2e(4) 3-7
Formed surfaces . . . . . . . . . . . . 3-2e(5) 3-7
Unusual or complex problems . . . . 3-2f 3-7
Chapter 4
Mixture Proportioning Considerations
Selection of Concrete Mixture
Proportions . . . . . . . . . . . . . . . . . . . 4-1 4-1
Basis for Selection of
Proportions . . . . . . . . . . . . . . . . . . 4-2 4-1
General . . . . . . . . . . . . . . . . . . . . 4-2a 4-1
Economy . . . . . . . . . . . . . . . . . . . 4-2b 4-1
Strength . . . . . . . . . . . . . . . . . . . 4-2c 4-1
Durability . . . . . . . . . . . . . . . . . . 4-2d 4-1
Placeability . . . . . . . . . . . . . . . . . 4-2e 4-1
Criteria for Mixture
Proportioning . . . . . . . . . . . . . . . . . 4-3 4-2
General . . . . . . . . . . . . . . . . . . . . 4-3a 4-2
Proportioning criteria . . . . . . . . . . 4-3b 4-2
Maximum permissible w/c . . . . . 4-3b(1) 4-2
Structural concrete . . . . . . . . . . 4-3b(2) 4-2
Mass concrete . . . . . . . . . . . . . 4-3b(3) 4-2
Nominal maximum aggregate
size . . . . . . . . . . . . . . . . . . . . . 4-3b(4) 4-5
Water content . . . . . . . . . . . . . . 4-3b(5) 4-5
Cement content . . . . . . . . . . . . 4-3b(6) 4-6
Proportioning with pozzolans
or GGBF slag . . . . . . . . . . . . 4-3b(7) 4-6
Government Mixture Proportioning . . . 4-4 4-6
General . . . . . . . . . . . . . . . . . . . . 4-4a 4-6
Coordination between project, district
design personnel, and the division
laboratory . . . . . . . . . . . . . . . . . 4-4b 4-6
Sampling of materials . . . . . . . . . . 4-4c 4-7
Data supplied by division laboratory
to project . . . . . . . . . . . . . . . . . 4-4d 4-7
Adjustment of government mixture
proportions . . . . . . . . . . . . . . . . 4-4e 4-7
Evaluation of Contractor-Developed
Mixture Proportions . . . . . . . . . . . . . 4-5 4-8
General . . . . . . . . . . . . . . . . . . . . 4-5a 4-8
Reviewing contractor submittals . 4-5b 4-8
Minor structures . . . . . . . . . . . . 4-5b(1) 4-8
Cast-in-place structural concrete . 4-5b(2) 4-8
Chapter 5
Preparation of Plans and Specifications
Selection of Guide Specification
for Concrete . . . . . . . . . . . . . . . . . 5-1 5-1
General . . . . . . . . . . . . . . . . . . . . 5-1a 5-1
Guidelines for selection . . . . . . . . . 5-1b 5-1
Use of state specifications . . . . . . . 5-1c 5-1
Use of abbreviated specifications . . 5-1d 5-1
Guide Specification "Concrete (for Minor
Structures)", CW-03307 . . . . . . . . . 5-2 5-1
General . . . . . . . . . . . . . . . . . . . . 5-2a 5-1
Cementitious materials options . . . . 5-2b 5-1
Selection of compressive strength . . 5-2c 5-1
Selection of nominal maximum
aggregate size . . . . . . . . . . . . . . 5-2d 5-1
Finish requirements . . . . . . . . . . . 5-2e 5-2
Guide Specification "Cast-in-Place Structural
Concrete," CW-03301 . . . . . . . . . . . 5-3 5-2
General . . . . . . . . . . . . . . . . . . . . 5-3a 5-2
Testing of cementitious materials . . 5-3b 5-2
Admixtures and curing compounds . 5-3c 5-2
Testing of aggregate . . . . . . . . . . . 5-3d 5-2
Nonshrink grout . . . . . . . . . . . . . . 5-3e 5-2
Cementing materials option . . . . . . 5-3f 5-2
Specifying aggregate . . . . . . . . . . . 5-3g 5-3
Strength . . . . . . . . . . . . . . . . . . . 5-3h 5-3
Batch-plant capacity . . . . . . . . . . . 5-3i 5-3
Batch-plant controls . . . . . . . . . . . 5-3j 5-3
Concrete deposited in water . . . . . . 5-3k 5-3
Finishing unformed surfaces . . . . . 5-3l 5-3
Sheet curing . . . . . . . . . . . . . . . . 5-3m 5-3
Areas to be painted . . . . . . . . . . . . 5-3n 5-3
Finishing formed surfaces . . . . . . . 5-3o 5-3
Floor tolerance . . . . . . . . . . . . . . . 5-3p 5-3
Guide Specification "Mass Concrete,"
CW-03305 . . . . . . . . . . . . . . . . . . . 5-4 5-3
General . . . . . . . . . . . . . . . . . . . . 5-4a 5-3
Sampling of aggregates . . . . . . . . . 5-4b 5-4
Mixture proportioning studies . . . . 5-4c 5-4
Testing cementitious materials . . . . 5-4d 5-4
Surface requirements . . . . . . . . . . 5-4e 5-4
Class A finish . . . . . . . . . . . . . 5-4e(1) 5-4
Class AHV finish . . . . . . . . . . . 5-4e(2) 5-4
Class B finish . . . . . . . . . . . . . 5-4e(3) 5-4
iii

9. EM 1110-2-2000
1 Feb 94
Table of Contents (Continued)
Subject Paragraph Page Subject Paragraph Page
Class C finish . . . . . . . . . . . . . 5-4e(4) 5-4
Class D finish . . . . . . . . . . . . . 5-4e(5) 5-4
Absorptive form lining . . . . . . . 5-4e(6) 5-4
Appearance . . . . . . . . . . . . . . . . . 5-4f 5-4
Cementitious materials option . . . . 5-4g 5-4
Bid schedule for cementitious materials
option . . . . . . . . . . . . . . . . . . . . 5-4h 5-5
Retarder . . . . . . . . . . . . . . . . . . . 5-4i 5-5
Water reducers . . . . . . . . . . . . . . . 5-4j 5-5
Fine aggregate grading requirements 5-4k 5-5
Coarse aggregate grading
requirements . . . . . . . . . . . . . . . 5-4l 5-5
Batching and mixing plant . . . . . . . 5-4m 5-5
Type of plant . . . . . . . . . . . . . . 5-4m(1) 5-5
Capacity . . . . . . . . . . . . . . . . . 5-4m(2) 5-5
Preset mixes . . . . . . . . . . . . . . 5-4m(3) 5-6
Mixers . . . . . . . . . . . . . . . . . . 5-4m(4) 5-6
Conveying and placing . . . . . . . . . 5-4n 5-6
Conveyance methods . . . . . . . . . 5-4n(1) 5-6
Hot-weather mixing and placing . 5-4n(2) 5-6
Placing temperature . . . . . . . . . 5-4n(3) 5-6
Lift thickness . . . . . . . . . . . . . . 5-4n(4) 5-6
Placing concrete in unformed
curved sections . . . . . . . . . . . 5-4n(5) 5-6
Concrete deposited in water . . . . 5-4n(6) 5-6
Finishing . . . . . . . . . . . . . . . . . . . 5-4o 5-6
Unformed surfaces . . . . . . . . . . 5-4o(1) 5-6
Formed surfaces . . . . . . . . . . . . 5-4o(2) 5-6
Insulation and special protection . 5-4o(3) 5-6
Areas to be painted . . . . . . . . . . . . 5-4p 5-6
Setting of base plates and bearing
plates . . . . . . . . . . . . . . . . . . . . 5-4q 5-6
Measurement and payment . . . . . . 5-4r 5-7
Guide Specification "Formwork for Concrete,"
CW-03101 . . . . . . . . . . . . . . . . . . . 5-5 5-7
General . . . . . . . . . . . . . . . . . . . . 5-5a 5-7
Shop drawings . . . . . . . . . . . . . . . 5-5b 5-7
Sample panels . . . . . . . . . . . . . . . 5-5c 5-7
Forms . . . . . . . . . . . . . . . . . . . . . 5-5d 5-7
Form removal . . . . . . . . . . . . . . . 5-5e 5-7
Guide Specification "Expansion, Contraction,
and Construction Joints in Concrete,"
CW-03150 . . . . . . . . . . . . . . . . . . . 5-6 5-7
General . . . . . . . . . . . . . . . . . . . . 5-6a 5-7
Cost of testing . . . . . . . . . . . . . . . 5-6b 5-7
Guide Specification "Precast Prestressed
Concrete," CW-03425 . . . . . . . . . . . 5-7 5-7
General . . . . . . . . . . . . . . . . . . . . 5-7a 5-7
Air content . . . . . . . . . . . . . . . . . 5-7b 5-7
Tolerances . . . . . . . . . . . . . . . . . . 5-7c 5-7
Cement . . . . . . . . . . . . . . . . . . . . 5-7d 5-7
Aggregates . . . . . . . . . . . . . . . . . 5-7e 5-7
Finishing . . . . . . . . . . . . . . . . . . . 5-7f 5-7
Guide Specification "Preplaced Aggregate
Concrete," CW-03362 . . . . . . . . . . . 5-8 5-7
Chapter 6
Coordination Between Design and
Field Activities
Bidability, Constructibility, and
Operability Review . . . . . . . . . . . . . 6-1 6-1
General . . . . . . . . . . . . . . . . . . . . 6-1a 6-1
Review guidance . . . . . . . . . . . . . 6-1b 6-1
Engineering Considerations and Instructions
for Construction Field Personnel . . . 6-2 6-1
General . . . . . . . . . . . . . . . . . . . . 6-2a 6-1
Content . . . . . . . . . . . . . . . . . . . . 6-2b 6-1
Discussion by outline heading . . . . 6-2c 6-2
Introduction . . . . . . . . . . . . . . . 6-2c(1) 6-2
Cementitious materials requirements
or properties . . . . . . . . . . . . . 6-2c(2) 6-2
Aggregate requirements or
properties . . . . . . . . . . . . . . . 6-2c(3) 6-2
Other materials . . . . . . . . . . . . . 6-2c(4) 6-2
Concrete qualities required at various
locations within the structures . 6-2c(5) 6-2
Concrete temperature-control
requirements . . . . . . . . . . . . . 6-2c(6) 6-3
Cold-weather concrete
requirements . . . . . . . . . . . . . 6-2c(7) 6-3
Hot-weather concrete
requirements . . . . . . . . . . . . . 6-2c(8) 6-3
Contractor quality control and quality
government assurance . . . . . . . 6-2c(9) 6-3
Critical concrete placement
requirements . . . . . . . . . . . . . 6-2c(10) 6-3
Architectural requirements . . . . . 6-2c(11) 6-3
Finish requirements . . . . . . . . . . 6-2c(12) 6-3
Chapter 7
Preparation for Construction
Materials Acceptance Testing . . . . . . . 7-1 7-1
General . . . . . . . . . . . . . . . . . . . . 7-1a 7-1
Cement, pozzolan, and GGBF slag . 7-1b 7-1
Chemical admixtures . . . . . . . . . . 7-1c 7-1
Test of air-entraining admixtures 7-1c(1) 7-1
iv

10. EM 1110-2-2000
1 Feb 94
Table of Contents (Continued)
Subject Paragraph Page Subject Paragraph Page
Test of other chemical
admixtures . . . . . . . . . . . . . . . . 7-1c(2) 7-2
Tests of accelerators . . . . . . . . . 7-1c(3) 7-2
Aggregates - listed source . . . . . . . 7-1d 7-2
Aggregates - nonlisted source . . . . 7-1e 7-2
Aggregates - minor concrete jobs . . 7-1f 7-2
Mixture Proportioning . . . . . . . . . . . . 7-2 7-2
Concrete Plant and Materials . . . . . . . 7-3 7-3
Review of concrete plant drawings . 7-3a 7-3
Estimating plant capacity . . . . . . . . 7-3b 7-3
Aggregate storage, reclaiming, washing,
and rescreening . . . . . . . . . . . . . 7-3c 7-3
Concrete cooling plant capacity . . . 7-3d 7-4
Batching and Mixing Equipment . . . . 7-4 7-4
Checking compliance with specification
requirements . . . . . . . . . . . . . . . 7-4a 7-4
Scale checks . . . . . . . . . . . . . . . . 7-4b 7-4
Mixer blades and paddles . . . . . . . 7-4c 7-4
Recorders . . . . . . . . . . . . . . . . . . 7-4d 7-4
Batching sequence . . . . . . . . . . . . 7-4e 7-4
Mixer performance and
mixing time . . . . . . . . . . . . . . . . . 7-4f 7-4
Conveying Concrete . . . . . . . . . . . . . 7-5 7-5
General . . . . . . . . . . . . . . . . . . . . 7-5a 7-5
Buckets . . . . . . . . . . . . . . . . . . . . 7-5b 7-5
Truck mixers and agitators . . . . . . 7-5c 7-5
Nonagitating equipment . . . . . . . . 7-5d 7-5
Positive-displacement pump . . . . . . 7-5e 7-5
Belts . . . . . . . . . . . . . . . . . . . . . . 7-5f 7-5
Chutes . . . . . . . . . . . . . . . . . . . . 7-5g 7-5
Preparation for Placing . . . . . . . . . . . 7-6 7-6
General . . . . . . . . . . . . . . . . . . . . 7-6a 7-6
Earth foundations . . . . . . . . . . . . . 7-6b 7-6
Rock foundations . . . . . . . . . . . . . 7-6c 7-6
Cleanup of concrete surfaces . . . . . 7-6d 7-6
Placing equipment . . . . . . . . . . . . 7-6e 7-6
Vibrators . . . . . . . . . . . . . . . . . 7-6e(1) 7-6
Cold-weather and hot-weather
protection equipment . . . . . . . 7-6e(2) 7-6
Communication equipment . . . . . 7-6e(3) 7-6
Other equipment . . . . . . . . . . . . 7-6e(4) 7-7
Forms . . . . . . . . . . . . . . . . . . . . . 7-6f 7-7
Curing and protection . . . . . . . . . . 7-6g 7-7
Approval . . . . . . . . . . . . . . . . . . . 7-6h 7-7
Interim slabs on grade . . . . . . . . . . 7-6i 7-7
Chapter 8
Concrete Construction
Forms . . . . . . . . . . . . . . . . . . . . . . . 8-1 8-1
Types of materials . . . . . . . . . . . . 8-1a 8-1
Quality verification . . . . . . . . . . . . 8-1b 8-1
Form coating . . . . . . . . . . . . . . . . 8-1c 8-1
Placing . . . . . . . . . . . . . . . . . . . . . . 8-2 8-1
General . . . . . . . . . . . . . . . . . . . . 8-2a 8-1
Bedding mortar on rock foundations 8-2b 8-1
Mass concrete . . . . . . . . . . . . . . . 8-2c 8-1
Structural concrete . . . . . . . . . . . . 8-2d 8-2
Tunnel linings . . . . . . . . . . . . . . . 8-2e 8-2
Inverts . . . . . . . . . . . . . . . . . . . 8-2e(1) 8-2
Sidewalls and crown . . . . . . . . . 8-2e(2) 8-2
Consolidation . . . . . . . . . . . . . . . . 8-2f 8-2
Protection of waterstops . . . . . . . . 8-2g 8-2
Finishing . . . . . . . . . . . . . . . . . . . . . 8-3 8-2
Formed surfaces . . . . . . . . . . . . . . 8-3a 8-2
Unformed surfaces . . . . . . . . . . . . 8-3b 8-3
Ogee crest . . . . . . . . . . . . . . . . 8-3b(1) 8-3
Spillway aprons . . . . . . . . . . . . 8-3b(2) 8-3
Trapezoidal channel lining . . . . . 8-3b(3) 8-3
Surfaces exposed to high-velocity
flow of water . . . . . . . . . . . . . 8-3b(4) 8-3
Floors . . . . . . . . . . . . . . . . . . . 8-3b(5) 8-4
Tolerance requirements for surface
finish . . . . . . . . . . . . . . . . . . . . 8-3c 8-4
General . . . . . . . . . . . . . . . . . . 8-3c(1) 8-4
Control surface tolerance by
straightedge . . . . . . . . . . . . . . 8-3c(2) 8-4
Control floor tolerance by F-number
system . . . . . . . . . . . . . . . . . 8-3c(3) 8-4
Curing . . . . . . . . . . . . . . . . . . . . . . . 8-4 8-5
General . . . . . . . . . . . . . . . . . . . . 8-4a 8-5
Moist curing . . . . . . . . . . . . . . . . 8-4b 8-5
Membrane curing . . . . . . . . . . . . . 8-4c 8-5
Sheet curing . . . . . . . . . . . . . . . . 8-4d 8-5
Cold-Weather Concreting . . . . . . . . . . 8-5 8-6
General . . . . . . . . . . . . . . . . . . . . 8-5a 8-6
Planning . . . . . . . . . . . . . . . . . . . 8-5b 8-6
Protection system . . . . . . . . . . . . . 8-5c 8-6
Curing . . . . . . . . . . . . . . . . . . . . 8-5d 8-6
Accelerating early strength . . . . . . 8-5e 8-7
Hot-Weather Concreting . . . . . . . . . . . 8-6 8-7
General . . . . . . . . . . . . . . . . . . . . 8-6a 8-7
Planning . . . . . . . . . . . . . . . . . . . 8-6b 8-7
Alleviating measures . . . . . . . . . . . 8-6c 8-7
Placing temperature . . . . . . . . . . . 8-6d 8-8
Plastic-shrinkage cracks . . . . . . . . 8-6e 8-8
Effect on strength and durability . . 8-6f 8-8
Cooling . . . . . . . . . . . . . . . . . . . . 8-6g 8-9
Curing . . . . . . . . . . . . . . . . . . . . 8-6h 8-9
v

11. EM 1110-2-2000
1 Feb 94
Table of Contents (Continued)
Subject Paragraph Page Subject Paragraph Page
Chapter 9
Concrete Quality Verification and Testing
Quality verification . . . . . . . . . . . . . . 9-1 9-1
General . . . . . . . . . . . . . . . . . . . . 9-1a 9-1
Government quality assurance . . . . 9-1b 9-1
Quality assurance representative . 9-1b(1) 9-1
Testing technicians . . . . . . . . . . 9-1b(2) 9-1
Organization . . . . . . . . . . . . . . 9-1b(3) 9-2
Records . . . . . . . . . . . . . . . . . . 9-1b(4) 9-2
Required Sampling and Testing
for CQC and GQC . . . . . . . . . . 9-2 9-3
Aggregate grading . . . . . . . . . . . . 9-2a 9-3
Frequency . . . . . . . . . . . . . . . . 9-2a(1) 9-3
Size of samples . . . . . . . . . . . . 9-2a(2) 9-3
Aggregate quality - large project . . 9-2b 9-4
Free moisture on aggregates . . . . . 9-2c 9-4
Slump and air content . . . . . . . . . . 9-2d 9-4
Concrete temperature . . . . . . . . . . 9-2e 9-4
Compressive strength . . . . . . . . . . 9-2f 9-4
Purpose . . . . . . . . . . . . . . . . . . 9-2f(1) 9-4
Testing responsibility . . . . . . . . 9-2f(2) 9-5
Sampling plan . . . . . . . . . . . . . 9-2f(3) 9-5
Frequency and testing age . . . . . 9-2f(4) 9-5
Sampling and testing methods . . 9-2f(5) 9-5
Analysis of tests . . . . . . . . . . . . 9-2f(6) 9-5
Control criteria . . . . . . . . . . . . . 9-2f(7) 9-6
Prediction of later age strengths . 9-2f(8) 9-6
Nondestructive Testing . . . . . . . . . . . . 9-3 9-7
General . . . . . . . . . . . . . . . . . . . . 9-3a 9-7
Policy . . . . . . . . . . . . . . . . . . . . . 9-3b 9-7
Applicability . . . . . . . . . . . . . . . . 9-3c 9-7
Nondestructive testing methods . . . 9-3d 9-7
Rebound hammer . . . . . . . . . . . 9-3d(1) 9-7
Penetration resistance . . . . . . . . 9-3d(2) 9-7
Cast-in-place pullout tests . . . . . 9-3d(3) 9-8
Maturity method . . . . . . . . . . . . 9-3d(4) 9-8
Cores . . . . . . . . . . . . . . . . . . . 9-3d(5) 9-8
Pulse velocity method . . . . . . . . 9-3d(6) 9-8
Other methods . . . . . . . . . . . . . 9-3d(7) 9-9
Preplacement Quality Verification . . . . 9-4 9-9
Project Laboratory . . . . . . . . . . . . . . 9-5 9-9
General . . . . . . . . . . . . . . . . . . . . 9-5a 9-9
Space requirements . . . . . . . . . . . . 9-5b 9-9
Large-volume project . . . . . . . . 9-5b(1) 9-9
Other . . . . . . . . . . . . . . . . . . . 9-5b(2) 9-9
Equipment . . . . . . . . . . . . . . . . . . 9-5c 9-9
Large-volume project . . . . . . . . 9-5c(1) 9-9
Other . . . . . . . . . . . . . . . . . . . 9-5c(2) 9-10
Chapter 10
Special Concretes
General . . . . . . . . . . . . . . . . . . . . . . . 10-1 10-1
Preplaced-Aggregate Concrete . . . . . . . 10-2 10-1
General . . . . . . . . . . . . . . . . . . . . 10-2a 10-1
Applications . . . . . . . . . . . . . . . . 10-2b 10-1
Materials and proportioning . . . . . . 10-2c 10-1
Preplacing aggregate . . . . . . . . . . . 10-2d 10-2
Contaminated water . . . . . . . . . . . 10-2e 10-2
Preparation of underwater
foundations . . . . . . . . . . . . . . . . 10-2f 10-2
Pumping . . . . . . . . . . . . . . . . . . . 10-2g 10-2
Joint construction . . . . . . . . . . . . . 10-2h 10-2
Grouting procedure . . . . . . . . . . . . 10-2i 10-3
Horizontal layer . . . . . . . . . . . . 10-2i(1) 10-3
Advancing slope . . . . . . . . . . . . 10-2i(2) 10-3
Grout insert pipes and sounding
devices . . . . . . . . . . . . . . . . . 10-2i(3) 10-3
Finishing unformed surfaces . . . . . 10-2j 10-3
Underwater Concrete . . . . . . . . . . . . . 10-3 10-3
General . . . . . . . . . . . . . . . . . . . . 10-3a 10-3
Tremie concrete . . . . . . . . . . . . . . 10-3b 10-4
Pumped concrete for use
underwater . . . . . . . . . . . . . . . . 10-3c 10-4
Blockout Concrete . . . . . . . . . . . . . . . 10-4 10-5
General . . . . . . . . . . . . . . . . . . . . 10-4a 10-5
Blockout concrete proportions . . . . 10-4b 10-5
High-Strength Concrete . . . . . . . . . . . 10-5 10-5
General . . . . . . . . . . . . . . . . . . . . 10-5a 10-5
Definition . . . . . . . . . . . . . . . . . . 10-5b 10-5
Materials . . . . . . . . . . . . . . . . . . . 10-5c 10-5
Cement type . . . . . . . . . . . . . . . . 10-5d 10-5
Cement content . . . . . . . . . . . . . . 10-5e 10-6
Aggregates . . . . . . . . . . . . . . . . . 10-5f 10-6
Pozzolans . . . . . . . . . . . . . . . . . . 10-5g 10-6
Use of HRWRA . . . . . . . . . . . . . . 10-5h 10-6
Workability . . . . . . . . . . . . . . . . . 10-5i 10-6
Proportioning . . . . . . . . . . . . . . . . 10-5j 10-6
Material handling . . . . . . . . . . . . . 10-5k 10-6
Preparation for placing . . . . . . . . . 10-5l 10-7
Curing . . . . . . . . . . . . . . . . . . . . 10-5m 10-7
Testing . . . . . . . . . . . . . . . . . . . . 10-5n 10-7
Pumped Concrete . . . . . . . . . . . . . . . . 10-6 10-7
General . . . . . . . . . . . . . . . . . . . . 10-6a 10-7
Pump lines . . . . . . . . . . . . . . . . . 10-6b 10-7
Mixture proportions . . . . . . . . . . . 10-6c 10-7
Coarse aggregates . . . . . . . . . . . . . 10-6d 10-7
vi

12. EM 1110-2-2000
1 Feb 94
Table of Contents (Continued)
Subject Paragraph Page Subject Paragraph Page
Fine aggregates . . . . . . . . . . . . . . 10-6e 10-8
Slump . . . . . . . . . . . . . . . . . . . . . 10-6f 10-8
Admixtures . . . . . . . . . . . . . . . . . 10-6g 10-8
Pumpability tests . . . . . . . . . . . . . 10-6h 10-8
Planning . . . . . . . . . . . . . . . . . . . 10-6i 10-8
Other requirements . . . . . . . . . . . . 10-6j 10-8
Quality verification . . . . . . . . . . . . 10-6k 10-8
Fiber-Reinforced Concrete . . . . . . . . . 10-7 10-9
General . . . . . . . . . . . . . . . . . . . . 10-7a 10-9
Advantages and limitations . . . . . . 10-7b 10-9
Toughness . . . . . . . . . . . . . . . . . . 10-7c 10-9
Performance characteristics . . . . . . 10-7d 10-9
Mixture proportioning . . . . . . . . . . 10-7e 10-9
Batching and mixing . . . . . . . . . . . 10-7f 10-9
Placement . . . . . . . . . . . . . . . . . . 10-7g 10-10
Workability . . . . . . . . . . . . . . . . . 10-7h 10-10
Pumping . . . . . . . . . . . . . . . . . . . 10-7i 10-10
Other fibers . . . . . . . . . . . . . . . . . 10-7j 10-10
Effects of polypropylene fibers
on workability . . . . . . . . . . . . . . 10-7k 10-10
Use of polypropylene fibers . . . . . . 10-7l 10-10
Porous Concrete . . . . . . . . . . . . . . . . 10-8 10-10
General . . . . . . . . . . . . . . . . . . . . 10-8a 10-10
Types . . . . . . . . . . . . . . . . . . . . . 10-8b 10-10
Composition . . . . . . . . . . . . . . . . 10-8c 10-11
W/C considerations . . . . . . . . . . . . 10-8d 10-11
Durability . . . . . . . . . . . . . . . . . . 10-8e 10-11
Percent voids . . . . . . . . . . . . . . . . 10-8f 10-11
Proportioning porous concrete
mixtures . . . . . . . . . . . . . . . . . . 10-8g 10-11
Placement . . . . . . . . . . . . . . . . . . 10-8h 10-11
Flowing Concrete . . . . . . . . . . . . . . . . 10-9 10-11
General . . . . . . . . . . . . . . . . . . . . 10-9a 10-11
HRWRA . . . . . . . . . . . . . . . . . . . 10-9b 10-12
Proportioining flowing concrete . . . 10-9c 10-12
Flowing concrete fresh properties . . 10-9d 10-12
Flowing concrete hardened
properties . . . . . . . . . . . . . . . . . 10-9e 10-12
Silica-Fume Concrete . . . . . . . . . . . . . 10-10 10-12
General . . . . . . . . . . . . . . . . . . . . 10-10a 10-12
Properties of silica fume . . . . . . . . 10-10b 10-12
Effect on water demand and
bleeding . . . . . . . . . . . . . . . . . . 10-10c 10-12
Effect on cohesiveness . . . . . . . . . 10-10d 10-13
Effect on air entrainment . . . . . . . . 10-10e 10-13
Effect on plastic shrinkage . . . . . . 10-10f 10-13
Effect on strength and modulus
of elasticity . . . . . . . . . . . . . . . . 10-10g 10-13
Effect on permeability and durability 10-10h 10-13
Chapter 11
Concrete Report
General . . . . . . . . . . . . . . . . . . . . . . . 11-1 11-1
Policy . . . . . . . . . . . . . . . . . . . . . 11-1a 11-1
Author . . . . . . . . . . . . . . . . . . . . 11-1b 11-1
Timing . . . . . . . . . . . . . . . . . . . . 11-1c 11-1
Content . . . . . . . . . . . . . . . . . . . . . . . 11-2 11-1
Outline . . . . . . . . . . . . . . . . . . . . 11-2a 11-1
Detailed instruction . . . . . . . . . . . . 11-2b 11-1
Introduction . . . . . . . . . . . . . . . 11-2b(1) 11-1
Aggregate sources . . . . . . . . . . . 11-2b(2) 11-1
Aggregate production . . . . . . . . 11-2b(3) 11-1
Cementitious materials . . . . . . . 11-2b(4) 11-4
Chemical admixtures . . . . . . . . . 11-2b(5) 11-4
Concrete batching and mixing
plant . . . . . . . . . . . . . . . . . . . 11-2b(6) 11-4
Concrete mixtures used . . . . . . . 11-2b(7) 11-4
Equipment and techniques . . . . . 11-2b(8) 11-4
Concrete transportation and
placement . . . . . . . . . . . . . . . 11-2b(9) 11-4
Concrete curing and protection . . 11-2b(10) 11-4
Temperature control . . . . . . . . . 11-2b(11) 11-4
Special concretes . . . . . . . . . . . 11-2b(12) 11-4
Precast concrete . . . . . . . . . . . . 11-2b(13) 11-4
Quality verification and testing . . 11-2b(14) 11-4
Summary of test data . . . . . . . . 11-2b(15) 11-4
Special problems . . . . . . . . . . . 11-2b(16) 11-5
Appendix A
References
Appendix B
Abbreviations
Appendix C
Concrete Materials Design Memorandum
Appendix D
Alkali-Silica Aggregate Reactions
Appendix E
Alkali-Carbonate Rock Reactions
vii

13. EM 1110-2-2000
1 Feb 94
Chapter 1
Introduction
1-1. Purpose
The purpose of this manual is to provide information and
guidance for the investigation and selection of concrete
materials for civil works concrete structures. Elements
discussed include design studies and reports, preparation of
contract plans and specifications, construction preparation,
and concrete construction quality verification. Emphasis is
placed on the problems of concrete for hydraulic structures.
Roller-compacted concrete, shotcrete, rigid pavements,
architectural concrete, and concrete for repairs are not
included. These subjects are discussed in EM 1110-2-2006,
Roller-Compacted Concrete; EM 1110-2-2005, Standard
Practice for Shotcrete; TM 5-822-7, Standard Practice for
Concrete Pavements; EM 1110-1-2009, Architectural
Concrete; and EM 1110-2-2002, Evaluation and Repair of
Concrete Structures, respectively.
1-2. Applicability
This manual is applicable to all HQUSACE elements, major
subordinate commands, districts, laboratories, and field
operating activities having civil works responsibilities.
1-3. References
Applicable references are listed in Appendix A. The most
current versions of all references listed in paragraphs A-1
and A-2 should be maintained in all districts and divisions
having civil works responsibilities. The references should
be maintained in a location readily accessible to those
persons assigned the responsibility for concrete materials
investigations and concrete construction. Terms used in this
document are defined in ACI 116R.
1-4. Explanation of Abbreviations
Abbreviations used in this manual are explained in
Appendix B.
1-5. Engineering Responsibilities and
Requirements
This paragraph outlines the concrete-related engineering
responsibilities and requirements during the development of
a civil works project. A summary of these engineering
requirements is presented in Table 1-1. Deviations from the
requirements described in this paragraph are possible, and
such an option as progression from a feasibility report
directly to plans and specifications may be permissible.
Requests for exceptions or deviations should be made in
accordance with ER 1110-2-1150.
a. Reconnaissance phase. Concrete investigation is
generally not required during the reconnaissance phase.
However, the engineering effort and budget required for
concrete investigation during the feasibility phase should be
identified and included in the Feasibility Cost-Sharing
Agreement (FCSA).
b. Feasibility phase. During the feasibility phase, a
preliminary investigation, in accordance with the
requirements given in Chapter 2, should be conducted to
determine the potential sources and suitability of concrete
materials. The engineering effort during this phase should
be sufficient so that the baseline cost estimate with
reasonable contingency factors for concrete materials can be
developed. The potential sources and suitability of concrete
materials for the project should be documented in the
engineering appendix to the feasibility report (or in a
general design memorandum (GDM)) in accordance with
ER 1110-2-1150, Engineering and Design for Civil Works
Projects. Any special studies required during the
preconstruction engineering and design (PED) phase should
be identified. These special studies may include, but not be
limited to, thermal studies, abrasion-erosion studies, mixer
grinding studies, and cavitation studies. The budget and
schedules for these special studies and for the concrete
report should be included in the project management plan
(PMP).
c. Preconstruction engineering and design
phase. During the PED phase and prior to the preparation
of plans and specifications (P&S), a detailed engineering
investigation on concrete materials, including cementitious
materials, aggregates, water for mixing and curing, and
chemical admixtures, should be conducted in accordance
with the requirements given in Chapter 2. Concrete mixture
proportioning and concrete construction procedures should
be investigated in accordance with pertinent requirements in
Chapters 4 and 7, respectively. The results of these
investigations should be documented in a concrete/materials
design memorandum (DM). The scope and format for the
DM will vary depending on the quantities and criticality of
concrete involved as outlined in Appendix C. Any special
studies identified in the feasibility phase should be carried
out during the PED. The concrete plans and specifications
should be prepared in accordance with Chapter 5. For any
project which includes major concrete construction, a report
outlining the engineering considerations and providing
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14. EM 1110-2-2000
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Table 1-1
Concrete-Related Engineering Responsibilities and Requirements
Phase Engineering Efforts Document
Reconnaissance Identify engineering efforts and budget
required for concrete investigation
during the feasibility phase
Input to FCSA
Feasibility Preliminary investigations to determine
the potential sources and suitability of
concrete materials
Engineering appendix to Feasibility Report or
GDM
Identify the engineering requirements,
budget, and schedules for the special
studies required during PED.
Engineering appendix to Feasibility Report (or
GDM) and PMP
PED Detailed investigations on concrete
materials, preliminary mixture
proportioning, and concrete construction
procedures
Concrete materials DM
Perform special studies DM or special study reports
Prepare concrete P&S ’s P&S
Prepare engineering considerations and
instructions for field personnel
Report
Construction Develop, adjust, or evaluate mixture
proportions
Site visits and QV
Support for concrete claims and
modifications
Prepare concrete report Concrete Report
instruction for field personnel to aid them in the supervision
and quality verification (QV) of concrete construction
should be prepared in accordance with Chapter 6.
d. Construction phase. Engineering effort during the
construction phase generally includes development,
adjustment or evaluation of mixture proportions, or both,
site visits and QV, support for concrete claims and
modifications, and preparation of a concrete report. The
concrete construction QV requirements are given in
Chapter 9. The guidelines for preparing a concrete report
can be found in Chapter 11.
1-6. Delays in Contract Awards
If delays of 5 years or longer occur between the time of
completion of the relevant concrete materials DM and the
start of construction, it will be necessary to reconfirm the
validity of the findings of the DM immediately prior to the
issuance of P&S’s to prospective bidders. The availability
of the types and sources of cementitious materials should be
rechecked. If changes have occurred, it may be necessary
to conduct tests to determine the suitability of the currently
available cementitious materials in combination with the
available aggregates and present findings in supplements to
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15. EM 1110-2-2000
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the earlier concrete materials DM. Aggregate sources that
have not been used in the period between the aggregate
investigations and the preparation for the contract award
may be assumed to remain acceptable. Commercial
aggregates sources that have been used should be examined
to verify that adequate materials remain in the pit or quarry
and that the lithology has not changed as materials have
been removed. If significant changes have occurred, they
should be confirmed petrographically. Depending on the
results of the petrographic examination, it may be necessary
to reevaluate the aggregate source for suitability. The
results of such a reevaluation should be presented as a
supplement to the earlier concrete materials DM.
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16. EM 1110-2-2000
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Chapter 2
Investigation and Selection of Materials
2-1. Introduction
During the investigations for a civil works structure that
incorporates concrete, it is necessary to assess the
availability and suitability of the materials needed to
manufacture concrete with qualities meeting the structural
and durability requirements. Materials involved include
cementitious materials, fine aggregate, coarse aggregate,
water for mixing and curing, and chemical admixtures.
These investigations will result in a separate DM or a
portion of a DM, in accordance with Appendix C.
2-2. Cementitious Materials
a. General. The goal of the investigation of
cementitious materials should be to determine the suitability
and availability of the various types of cement, pozzolan,
and ground granulated blast-furnace (GGBF) slag for the
structures involved and to select necessary options that may
be needed with the available aggregates. In cases where
types or quantities of available cementitious materials are
unusually limited, it may be necessary to consider altered
structural shapes, changing the types of structure, altered
construction sequence, imported aggregates, or other means
of achieving an economical, serviceable structure.
b. Types. The following types of cementitious
material should be considered when selecting the materials:
(1) Portland cement. Portland cement and air-
entraining portland cement are described in American
Society for Testing and Materials (ASTM) C 150
(CRD-C 201).
(2) Blended hydraulic cement. The types of blended
hydraulic cements are described in ASTM C 595
(CRD-C 203). ASTM Type I (PM) shall not be used;
reference paragraph 4-3b(7) of this manual.
(3) Pozzolan. Coal fly ash and natural pozzolan are
classified and defined in ASTM C 618 (CRD-C 255).
(4) GGBF slag. GGBF slag is described in ASTM C
989 (CRD-C 205).
* Test methods cited in this manner are from the American Society for
Testing and Materials Annual Book of ASTM Standards (ASTM 1992)
and from Handbook of Concrete and Cement (U.S. Army Engineer
Waterways Experiment Station (USAEWES) 1949), respectively.
(5) Other hydraulic cements.
(a) Expansive hydraulic cement. Expansive hydraulic
cements are described in ASTM C 845 (CRD-C 204).
(b) Calcium-aluminate cement. Calcium-aluminate
cements (also called high-alumina cement) are characterized
by a rapid strength gain, high resistance to sulfate attack,
resistance to acid attack, and resistance to high temperatures.
However, strength is lost at mildly elevated temperatures
(e.g. >85 °F) in the presence of moisture. This negative
feature makes calcium-aluminate cement impractical for
most construction. It is used predominantly in the
manufacture of refractory materials.
(c) Proprietary high early-strength cements. Cements
are available that gain strength very rapidly, sometimes
reaching compressive strengths of several thousand pounds
per square in. (psi) in a few hours. These cements are
marketed under various brand names. They are often not
widely available, and the cost is much higher than portland
cement. The extremely rapid strength gain makes them
particularly suitable for pavement patching.
(6) Silica fume. Silica fume is a pozzolan. It is a
byproduct of silicon and ferro-silicon alloy production.
Silica fume usually contains about 90 percent SiO2 in
microscopic particles in the range of 0.1 to 0.2 µm. These
properties make it an efficient filler as well as a very
reactive pozzolan. Silica fume combined with a high-range
* water reducer is used in very high-strength concrete. Silica
fume is described in ASTM C1240 (CRD-C270). Detailed
information can be found in paragraphs 2-2d(5) and 10-10.*
(7) Air-entraining portland cement. Air-entraining
portland cement is only allowed for use on structures co-
vered by the specifications for "Concrete for Minor Struc-
tures," CW-03307. Air-entraining admixtures are used on
all other Corps civil works structures since this allows the
air content to be closely controlled and varied if need be.
c. Selection of cementitious materials.
(1) General. The selection of one or several suitable
cementitious materials for a concrete structure depends on
the exposure conditions, the type of structure, the
characteristics of the aggregate, availability of the
cementitious material, and the method of construction.
(2) Type of structure. The type of structure, i.e. mass
or structural, provides an indication of the category of
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17. EM 1110-2-2000
1 Feb 94
concrete that the structure may contain. Mass concrete is
defined as any volume of concrete with dimensions large
enough to require that measures be taken to cope with
generation of heat from hydration of the cementitious
materials and attendant volume change to minimize
cracking. A gravity dam and a navigation lock are
examples of massive structures. Structural concrete is
defined as concrete which will normally be placed in
reinforced structural elements such as beams, columns,
walls, and slabs that have dimensions such that heat
generation is not a problem. Many features of a structure
will fall between the two extremes of being either strictly
massive or structural, and the designer will need to decide
if measures to limit or mitigate the heat generation will be
required. For example, reinforced walls and slabs of 4- to
6-ft thickness in a pumping station that contains 3,000- to
5,000-psi concrete would probably generate sufficient heat
that measures should be taken to limit either the peak
temperature of the concrete or the rate at which heat is lost
from the concrete after the peak temperature is reached.
The factors that affect the amount of heat that is generated
and the peak temperature that the concrete will reach are the
amount and type of cementitious materials in the concrete,
the size of the placement, and the initial placing
temperature.
(a) Table 2-1 lists cementitious materials that should
be investigated for availability and suitability, according to
the type of structure. Other more specialized cementitious
materials, such as Type V portland cement or proprietary
high-early strength cement, should be investigated if needed.
(b) Specification details. Type II cement is described
by ASTM C 150 (CRD-C 201) as a cement for use when
moderate sulfate resistance or moderate heat of hydration is
desired. The heat-of-hydration part of this description
requires that the 70-calorie/gram optional limit be specified.
Many Type II cements evolve heat at rates comparable to
those of Type I cements. The chemical requirement which
is in ASTM C 150 for the purpose of limiting heats of
hydration is not a satisfactory means of assuring reduced
heat of hydration and should not be used. Neither Type IV
portland cement nor Type P portland-pozzolan cement are
generally available at the present time. Both also exhibit
very low rates of strength gain. These characteristics should
be addressed in the concrete materials DM prior to
specifying either type. ASTM C 989 (CRD-C 205) includes
a provision for three grades of GGBF slag, grade 120,
which contributes to the fastest strength development, grade
100 which is an intermediate grade, and grade 80 which
contributes least to strength development. However, at
present, only grade 120 is available. Generally, if other
grades were available, grade 80, 100, or 120 should be
considered for use in mass concrete, and grades 100 and
120 should be considered for use in structural concrete.
(3) Other requirements.
(a) General. The investigation of cementitious
materials must include an assessment of the impact on cost
and availability of special requirements or options.
Provisions that limit the heat of hydration, provide sulfate
resistance, limit the alkali content, or control false set should
be invoked based on a demonstrated need for cement having
these characteristics.
(b) Sulfate exposures. Precautions against the
potentially harmful effects of sulfate will be specified when
concrete is to be exposed to seawater or the concentration
of water-soluble sulfate (SO4) in soil or in fresh water that
will be in contact with the concrete (as determined by
CRD-C 403 and 408) is greater than 0.10 percent or 150
parts per million (ppm,) respectively. Concentrations higher
than these will be classified as representing moderate or
severe potential exposures according to the criteria shown in
Table 2-2. The precautions to be specified will vary with
the availability and anticipated costs of materials and with
other factors. Where moderate attack is to be resisted,
moderate sulfate-resisting cement (Type II, Type III with the
optional 8 percent limit on C3A invoked, Type IP(MS),
Type IS(MS), or Type P(MS)) should be specified. In
seawater where no greater precautions than moderate are
needed, the 8-percent limit on C3A may be increased to 10
percent if the water-cement ratio (w/c) of the concrete is
kept below 0.45 by mass and the concrete will be
permanently submerged in seawater. If moderate sulfate-
resisting cement is not economically available, concrete that
is resistant to moderate attack may be made by using Type
I cement having not more than 10 percent C3A or Types IS
or IP which contain an adequate amount of suitable Class F
pozzolan or slag or to which additional Class F pozzolan or
slag is added. Performance tests must be conducted to
determine the suitability of any substitutes for sulfate-
resistant cement. If straight portland cement is proposed,
the test method is described in ASTM C 452 (CRD-C 232).
If a blend of portland cement and pozzolan or a blended
hydraulic cement is proposed, the test method is ASTM C
1012 (CRD-C 211). Where severe attack is to be resisted,
highly sulfate-resistant cement (Type V, Type III with
5 percent limit on C3A) should be specified and used unless
problems of cost or availability are encountered, in which
case other materials as outlined above should be taken.
Additional information may be obtained from American
Concrete Institute (ACI) 201.2R.
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18. EM 1110-2-2000
1 Feb 94
Table 2-1
Guide for Selection of Cementitious Materials According to Type Structure
Cementitious Material Mass Concrete Structural Concrete
Portland cement:
Type I X
Type II X X
Type II with heat of
hydration 70 cal/g or less
X X
Type I with pozzolan X
Type II with pozzolan X X
Type I with GGBF slag X
Type II with GGBF slag X X
Type III X
Type IV X
Blended hydraulic cements:
Type IS(MH) X X
Type IS X
Type IP(MH) X X
Type IP X
Type P X
Type P(LH) X
Type I(SM) X
Type I(SM), (MH) X
Type S, with Type I or Type II
Portland cement
X
Table 2-2
Guide for Determining Sulfate Exposure Condition
Exposure condition
SO4 concentration,
Fresh water
SO4 concentration,
Soil, %
Moderate 150 - 1,500 ppm 0.10 - 0.20
Severe >1,500 ppm >0.20
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19. EM 1110-2-2000
1 Feb 94
(c) False set. False set is one type of the abnormal
premature stiffening of cement within a few minutes of
mixing with water. Remixing of the concrete after a few
minutes of maintaining the mixer at rest or a longer initial
mixing time will restore the plasticity of the mixture, and it
will then set and gain strength normally. False set normally
does not occur when ready-mix trucks are used to transport
concrete because of the length of the mixing cycle. When
such lengthy mixing or a remix step, as described above, is
impractical, then the optional requirement limiting false set
in ASTM C 150 (CRD-C 201) should be invoked. When
premature stiffening cannot be overcome by additional
mixing, it is probably "flash set" due to inadequate
retardation of the cement during manufacture.
(d) Cement-admixture interaction. Some cement-
admixture combinations show no tendency to cause early
stiffening when tested according to ASTM C 451 (CRD-C
259) but will cause early stiffening when used with some
water-reducing admixtures. The phenomenon can be
detected by testing the cement and admixture proposed for
use according to ASTM C 451. Also see paragraph 2-5 on
chemical admixtures.
(e) Alkali reactivity. The potential for deleterious
reactivity of the alkalies in the cement with the aggregate
should be evaluated as outlined in Appendixes D and E of
this manual. If the aggregates are potentially reactive,
paragraph D-6 presents options, including disapproval of the
aggregate source, use of low-alkali cements, or use of
GGBF slag or pozzolans.
(f) Heat of hydration. The heat of hydration should be
limited in those cases where thermal strains induced on
cooling of the concrete are likely to exceed the strain
capacity of the concrete in the structure. This is
accomplished by specifying the available option for limiting
the heat of hydration for Type II portland cement or using
Type IV cement, if available. For blended hydraulic
cements, the heat of hydration is limited by specifying the
suffix (MH) for Type IS, I(SM), IP, S, and (LH) for Type
P. The replacement of a portion of the portland cement or
in some cases blended hydraulic cement with a pozzolan or
GGBF slag should always be considered. The heat
generation of each proposed cement type and each
combination of cement and pozzolan or slag should be
determined. The amount of heat generated should be equal
to or less than the amount generated by the Type II with
heat-of-hydration option which is also normally specified.
(4) Requirements for use of other hydraulic cements.
(a) Expansive hydraulic cement. Expansive cements
have been used in floor slabs, in the top lifts of some lock
walls, and in the lining slab of spillway channels to reduce
shrinkage cracking. The applications have generally been
accomplished in closely controlled situations and after
extensive investigation. Additional reinforcement is usually
required to control the expansion. Since the use of
expansive cements in water-control structures is far from
common, its proposed use will require a comprehensive
investigation to be included in the concrete-materials DM.
(b) High-alumina cement. High-alumina cement is not
normally used in civil works structures and should be
considered only in those locations which justify its added
cost and after investigating the possible effects of its
tendency to lose strength when exposed to heat and
moisture. Its use should be preceded by a comprehensive
investigation which is made a part of the concrete materials
DM.
(c) Proprietary high early-strength cements. Cements
that develop high strength within a few hours are often
considered for use in cold weather applications or for repair
applications, or both, that are required to bear load soon
after finishing. The investigation that precedes its use
should determine availability and the characteristics of the
available material. The results of the investigation should
be included in the concrete materials DM.
(5) Pozzolans. The classes of pozzolans most likely
to be available are classes F and C fly ash and silica fume.
Class N may be considered at those sites where a source of
natural pozzolan is available.
(a) Regulations governing use of fly ash. The Solid
Waste Disposal Act, Section 6002, as amended by the
Resource Conservation and Recovery Act of 1976, requires
all agencies using Federal funds in construction to allow the
use of fly ash in the concrete unless such use can be shown
to be technically improper. The basis of this regulation is
both energy savings and waste disposal, since most fly ash
in use today is the result of the burning of coal for electrical
power.
(b) General. The use of pozzolan should be
considered coincident with the consideration of the types of
available cements. Portland cement to be used alone should
always be considered in the specifications as well as
blended hydraulic cements or the combination of portland
cement with slag cement or pozzolan unless one or the latter
is determined to be technically improper. Classes F and C
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20. EM 1110-2-2000
1 Feb 94
fly ash are generally accepted on all Corps of Engineers’
(CE) civil works projects, and their use should be allowed
in all specifications unless there are technical reasons not to
do so.
(c) Class F pozzolan. Class F pozzolan is a fly ash
usually obtained from burning anthracite or bituminous coal
and is the class of fly ash that has been most commonly
used to date. It must contain at least 70.0 percent of
Si02 + Al203 + Fe203 by chemical analysis.
(d) Class C pozzolan. Class C pozzolan is a fly ash
that is usually obtained from the burning of lignite or
subbituminous coal. It must contain at least 50.0 percent
of Si02 + Al203 + Fe203 .
(e) Other considerations. Class C fly ashes often
contain considerably more alkalies than do Class F fly
ashes. However, when use of either class in applications
where alkali-aggregate reaction is likely, the optional
available alkali requirement of ASTM C 618 (CRD-C 255)
should be specified. Use of Class F fly ash in replacement
of portland cement results in reduction of heat of hydration
of the cementitious materials at early ages. Use of Class C
fly ash in the same proportions usually results in
substantially less reduction in heat of hydration. An
analysis of the importance of this effect should be made if
Class C fly ash is being considered for use in a mass
concrete application. See paragraph 3-2b, "Thermal
Studies." Class F fly ash generally increases resistance to
sulfate attack. However, if the portland cement is of high
C3A content, the amount of improvement may not be
sufficient so that the combined cementitious materials are
equivalent to a Type II or a Type V portland cement. This
can be determined by testing according to ASTM C 1012
(CRD-C 211). Class C fly ashes are quite variable in their
performance in sulfate environments, and their performance
should always be verified by testing with the portland
cement intended for use. Both Class F and Class C fly
ashes have been found to delay for initial and final set.
This retarding action should be taken into consideration if
important to the structure. Most Class C and Class F fly
ashes are capable of reducing the expansion from the alkali-
silica reaction. Use of an effective fly ash may eliminate
the need to specify low-alkali cement when a reactive
aggregate is used. The effectiveness of the fly ash must be
verified by ASTM C 441 (CRD-C 257). For additional
information, see Appendixes D and E.
(f) Class N pozzolan. Class N is raw or calcined
natural pozzolans such as some diatomaceous earths, opaline
cherts, tuffs, and volcanic ashes such as pumicite.
(g) Silica fume. Silica fume is a pozzolan. It is a
byproduct of the manufacture of silicon or silicon alloys.
The material is considerably more expensive than other
pozzolans. Properties of silica fume vary with the type of
silicon or silicon alloy produced, but in general, a silica
fume is a very finely divided product and consequently is
used in concrete in different proportions and for different
applications than are the more conventional pozzolans
discussed in the previous paragraphs. Applications for
which silica fume is used are in the production of concrete
having very high strengths, high abrasion resistance, very
low permeability, and increased aggregate bond strength.
However, certain precautions should be taken when
specifying silica-fume concretes. Use of silica fume
produces a sticky paste and an increased water demand for
equal slump. These characteristics are normally
counteracted by using high-range water-reducing admixtures
(HRWRA) to achieve the required slump. This
combination, together with an air-entraining admixture, may
cause a coarse air-void system. The higher water demand
for silica-fume concrete greatly reduces or eliminates
bleeding, which in turn tends to increase the likelihood of
plastic shrinkage cracking. Therefore, steps should be taken
as early as possible to minimize moisture loss, and the
curing period should be increased over that required for
conventional concrete. For additional information, see
paragraph 10-10i.
d. Availability investigation of cementitious materials.
(1) General. Following the investigation outlined
previously in paragraph 2-1c to determine the technical
requirements of the cementitious materials for a project, it
is necessary to assess availability of those materials in the
project area. Technical requirements to use a certain type
or kind of cementitious material to assure long-term
durability and serviceability of the structure shall not be
compromised because of the cost of obtaining the material.
All cementitious materials should be furnished by the
Contractor. The contract specifications should allow the
Contractor maximum flexibility to provide cementitious
materials that meet the technical requirements for the
project. The investigation should cover an area sufficient to
provide at least two sources of each cementitious material
to provide price competition. An estimate of the cost per
ton of each material delivered to the project should be
secured from each producer. The key objective of the
availability investigation is to ensure that materials meeting
the technical requirements can be obtained by the
Contractor.
(2) Portland cement and blended hydraulic cements.
The availability of the technically acceptable portland
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21. EM 1110-2-2000
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31 Jul 94
cement and blended hydraulic cement types must be invest-
igated prior to listing materials in the DM or the contract
specifications. Any optional physical or chemical require-
ments from ASTM C 150 (CRD-C 201) or ASTM C 595
(CRD-C 203) that are to be invoked by the designer must be
considered during the investigation. For example, Type II
cement or Type IP blended hydraulic cement may be readily
available in the project area, but when the heat-of-hydration
option is invoked from ASTM C 150 for portland cement or
from ASTM C 595 for blended hydraulic cement, the
availability may be severely reduced. Producers in the
project area should be queried about their current production
and also about their ability and willingness to produce
material that meets any optional physical or chemical
requirements that the designer deems necessary.
(3) Pozzolans. The availability of technically
acceptable pozzolans, both natural pozzolans and fly ashes,
must be investigated prior to listing materials in the contract
specifications. Normally, only commercial sources of
natural pozzolan and fly ash that are economically viable for
use on the project will need to be investigated.
Undeveloped sources of natural pozzolans should not be
investigated unless there are no other sources of pozzolan
available. CECW-EG should be contacted for guidance in
evaluating an undeveloped source of natural pozzolan. The
availability investigation should include any optional
chemical or physical options from ASTM 618 (CRD-C 255)
that the designer needs to invoke for technical reasons.
Producers in the project area should be queried about their
production and material properties and also about their
ability and willingness to produce material that meets any
optional requirements that the designer deems necessary. It
should be stressed that the uniformity requirement in
ASTM 618 will be required.
(4) GGBF slag. The availability of technically
acceptable GGBF slag must be investigated prior to listing
it in the contract specifications. Availability is presently
limited and only Grade 120 material is being produced.
GGBF slag must meet the requirements of ASTM C 989
(CRD-C 205).
(5) Silica fume. Silica fume is generally available
only from national distributors as a proprietary material. It
* is a relatively expensive material. Therefore, it is rarely
used in mass concrete structures but more likely in structural
concrete and shotcrete applications. When specifying silica
fume, the optional requirement of specific surface area in
ASTM C 1240 Table 4 should be invoked in all cases. The
optional Table 2 in ASTM C 1240 should be used only if
low alkali cement is required. The uniformity requirement
in Table 4 should be invoked when concrete is air-entrained.
The sulfate resistance expansion requirement in Table 4
need not be included except in areas where sulfate attack is
expected. All other optional requirements in Table 4 need
not be specified unless past experiences or environment
conditions justify these tests. *
2-3. Aggregates
a. General. One of the most important factors in
establishing the quality and economy of concrete is a
determination of the quality and quantity of aggregates
available to the project. Preliminary investigation to
determine potential aggregate sources should be performed
during the feasibility phase, and detailed investigations
should be performed during the PED prior to issuance of
P&S’s. All sources investigated during the PED should be
documented in the appropriate DM, and those sources found
capable of producing aggregates of suitable quality should
be listed for the Contractor’s information in the
specifications. Ideally, the sources investigated should be
within a few miles of the project; however, depending on
the quality of aggregates required and the availability of
transportation, aggregates may be transported a considerable
distance. Not all sources within a certain distance of a
project need be investigated, but representative sources from
various kinds of sources in the vicinity must be evaluated to
establish the quality of aggregates that can be produced.
The investigation should be comprehensive enough to assure
that more than one source of each aggregate type and size
is available to the Contractor. The decision of whether or
not to investigate a potential source should not be based on
the grading of materials currently stockpiled at the source
but should be based on determining the quality of the
aggregate from the source or formation. The
Contractor/producer should be given the opportunity during
construction to adjust his processing to meet the grading
specified. The investigation will result in a list of aggregate
qualities that are required for the project and an acceptance
limit for each quality. The aggregate qualities and their
respective limits must be documented in a DM and will be
used in preparation of specifications for the project.
(1) Sources of aggregate (Government or commercial).
The decision to investigate a Government source or only
commercial sources is based on appraisal of the economic
feasibility of an onsite source when compared to commercial
sources that contain aggregate of adequate quality and that
are within economic hauling distance of the project. The
appraisal should also consider the environmental
consequences of opening and restoring the Government site.
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22. EM 1110-2-2000
1 Feb 94
If a Government source is investigated, it will be owned or
controlled by the Government and will be made available to
the Contractor for the production of aggregate. The
presence of a Government source does not preclude the
investigation of commercial sources that appear to be
economically feasible. All sources investigated will be
documented in the appropriate DM.
(2) Minor structures. For minor structural projects,
the source of aggregate need not be listed since a quality
requirement is specified by reference to ASTM C 33
(CRD-C 133). Before specifications are issued, the
availability of aggregate meeting these requirements should
be determined. If none are economically available to the
project, then the specifications should be altered to allow the
use of the specification under which most of the satisfactory
aggregate in the area is produced, whether that be a state or
local specification.
b. Availability investigation.
(1) General. The objectives of the availability
investigation are to determine the required aggregate quality
for the project, the quality of the aggregate available to the
project, and that sufficient quantity of the required quality
is available. The required aggregate quality is stated in the
appropriate DM as a list of aggregate properties and their
respective acceptance test limits. Preliminary investigations
to determine the potential sources and the required aggregate
quality shall be performed during the feasibility phase and
the results documented in the engineering appendix to the
feasibility report. During the PED, field explorations and
sampling and testing of aggregates should be initiated based
on the work previously completed in the feasibility report.
This activity should be continued with an increasingly
expanded scope through the completion of the concrete
materials DM. If satisfactory Technical Memorandum No.
6-370, "Test Data, Concrete Aggregates and Riprap Stone in
Continental United States and Alaska" (USAEWES 1953),
data are available and less than 5 years old, it will not be
necessary to repeat the sampling and testing of those sources
for which such data are available. See Appendix C for
further guidance on the scope of the investigation.
(2) Service records. Service records can be of great
value in establishing the quality of an aggregate where
reliable information on the materials used to produce the in
situ concrete, construction procedures, and job control are
available. The service record must be of sufficient time to
assure that possible deleterious processes have had time to
manifest themselves and the existing structure must be in
the same environment that the proposed structure will be
subjected to. Photographs should be used to document the
condition of the in situ concrete.
(3) Field exploration and sampling of undeveloped
sources. In undeveloped potential quarries, field
explorations should consist of a general pattern of core
borings arranged to reveal the characteristic variations and
quality of material within the deposit. Representative
portions of the cores should be logged in detail and should
be selected for laboratory testing in accordance with
CRD-C 100. In addition to the small holes, large calyx drill
holes should be used to obtain large samples for processing
into aggregate similar to that required for the project,
unless a test quarry or test pit is to be opened. Additional
information on the exploration of undeveloped quarry
sources is available in EM 1110-1-1804, "Geotechnical
Investigations," and EM 1110-2-2302, "Construction with
Large Stone," and these references should be consulted prior
to undertaking an investigation. During PED, for a source
of crushed stone for a large project, a test quarry should be
opened and samples tested to assure that the required quality
is available. In the case of undeveloped alluvial deposits,
explorations should consist of a sufficient number of test
pits, trenches, and holes to indicate characteristic variations
in quality and quantity of material in the deposit. Grading
of materials in alluvial deposits should be determined to
establish grading trends within the deposits. Representative
samples of materials should be selected for laboratory
testing in accordance with CRD-C 100. Procedures for
making subsurface explorations are described in
EM 1110-1-1804, "Geotechnical Investigations."
(4) Field exploration and sampling of developed
sources. In commercial sources, a thorough geologic
evaluation should be made of the deposit from which the
raw materials are being obtained to determine the extent of
the deposit and whether or not material remaining in the
deposit may be expected to be essentially the same as that
recovered from the source at the time of the examinations.
In quarries and mines, working faces should be examined,
logged, sampled, photographed, and when considered
necessary, mapped. When available, results of and samples
from subsurface explorations performed by the owner should
be examined and evaluated. Where no subsurface
information is available and proper appraisal cannot be
made without it, arrangements should be made with the
owner to conduct the necessary subsurface explorations.
The primary source of samples for quality evaluation testing
should be from material produced at the time of the
investigation. These samples should be supplemented by
samples from working faces and subsurface explorations.
All samples should be taken in accordance with
CRD-C 100.
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23. EM 1110-2-2000
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(5) Testing potential aggregate sources. During the
PED phase, there should be sufficient testing to define the
quality of aggregates available within an economic hauling
distance of the project. The sampling and testing program
should be designed to evaluate geologic formations,
deposits, strata, or rock type available to the project. It is
not necessary to sample and test all producers within the
economic hauling distance of the project.
(6) Evaluating aggregate qualities.
(a) Significance of test results. Aggregate quality
cannot be measured by fixed numbers from laboratory test
results only. These results should be used as indicators of
quality rather than as positive numerical measures of
quality. An aggregate may still be considered acceptable for
a given project even though a portion of the test results fall
outside the conventional limits found in reference standards
such as ASTM C 33 (CRD-C 133). Results of individual
tests should be considered and the final judgment should be
based on overall performance, including service records
where available. The cost of obtaining aggregates of the
quality necessary to assure durability during the life of the
project should not be a factor in establishing the required
quality. The incremental cost of obtaining quality
aggregates during initial construction is always less than the
cost of repairs if concrete deteriorates during the service life
of the project due to aggregate deficiencies. Detailed
discussions of the interpretation of aggregate test data can
be found in ACI 221R and EM 1110-2-2302, "Construction
with Large Stone." See also the discussion in paragraph
2-3b(9)(b), "Acceptance Criteria."
(b) Petrographic examination (ASTM C 295 (CRD-C
127)). Results of a petrographic examination should be
used both for assessing the suitability of materials and for
determining what laboratory tests may be necessary to
evaluate the suitability of materials for use as concrete
aggregate. Petrographic examination is performed for two
purposes: (1) lithologic and mineralogic identification and
classification and (2) determination of composition, physical,
and chemical characteristics. From this examination, a
description of material should be written and a preliminary
estimate of the general quality of the material should be
made. It is possible to identify the presence of constituents
that are capable of reacting with the alkalies in cement from
petrographic examination. When such constituents are
identified, other investigations, including the Quick
Chemical Test (ASTM C 289 (CRD-C 128)) or Mortar-Bar
Test (ASTM C 227 (CRD-C 123)), or both, should be
performed to determine their potential reactive effects.
Table 2-3 lists the testing property, testing method, and
comments regarding the testing.
(c) Specific gravity (ASTM C 127; ASTM C 128).
Specific gravity of aggregates is necessary for calculating
the mass for a desired volume of material. It has no clearly
defined significance as a measure of suitability of material
for use as concrete aggregate. Aggregates with specific
gravity below 2.4 are usually suspected of being potentially
unsound and, thus, not suited for use in the exposed portions
of hydraulic structures in moderate-to-severe exposures.
However, these materials may still be used if their
performance in freezing-and-thawing tests is acceptable.
Low specific gravity has been indicative of poor quality in
porous chert gravel aggregates having high absorption.
Therefore, it may be necessary to set a limit on the
permissible amount of material lighter than a given specific
gravity when selecting chert gravel aggregates for use in
hydraulic structures in moderate or severe environment.
The specific gravity limit and the permissible amount lighter
than the limit should be established on the basis of results
of laboratory freezing-and-thawing tests.
(d) Absorption (ASTM C 127; ASTM C 128).
Absorption is determined primarily as an aid in estimating
amounts of water in aggregates for laboratory and field
control of amount of mixing water used in the concrete.
Absorption data are generally believed to be somewhat
indicative of the probable influence of aggregates on the
durability of concrete exposed to freezing and thawing when
subject to critical saturation. However, test results have
indicated that this premise must be used with caution in
assessing the quality of material. High absorption in
aggregates may be an indication of potential high shrinkage
in concrete and may need further investigation. However,
absorption alone should not be considered significant as a
measure of suitability of a material for use as concrete
aggregate.
(e) Organic impurities (ASTM C 87; ASTM C 40).
The test for presence of organic impurities should be used
primarily as warning that objectionable amounts of organic
impurities may be present in the aggregates. Objectional
amounts of organic matter will usually show "darker than
No. 3" in the ASTM C 40 test. Primary dependence should
be placed on the mortar strength tests as a basis for judging
whether or not objectionable amounts of organic impurities
are present in natural fine aggregate. Natural fine aggregate
showing the presence of organic matter and producing
mortar strength of less than 95 percent of those produced by
the same aggregate after washing with sodium hydroxide to
remove organic matter should not be selected for use unless
it is evident that the material can be adequately processed to
remove impurities.
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24. EM 1110-2-2000
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Table 2-3
Standard Procedures for Obtaining Information on Aggregate Quality
During the Preconstruction Engineering and Design Phase
Testing Property Testing Method* Comments
Composition and
identification
ASTM C 295 This petrographic examination is recommended for all aggregate evaluation and should
be the basis for the determination of other procedures required.
Specific gravity and
absorption
ASTM C 127
ASTM C 128
Density will affect the density of concrete. In general, higher absorption of coarse
aggregate may indicate less F/T resistance (CRD-C 107 and 108, respectively).
Organic impurities ASTM C 40
ASTM C 87
Too much impurity will affect the concrete strength. ASTM C 87 (CRD-C 116) should be
performed if there are objectionable amounts of organic impurities (CRD-C 121 and 116,
respectively).
Soft constituents CRD-C 141
CRD-C 130
Soft materials in fine aggregate will affect concrete strength and workability. Soft
particles in coarse aggregate will affect the bonding with cement.
Clay lumps and friable
particles
ASTM C 142 Clay lumps and friable particles will affect concrete strength and workability (CRD-C
142).
Lightweight particles ASTM C 123 Lightweight particles will affect the density of concrete (CRD-C 122).
Particle shape ASTM D 4791
CRD-C 120
ASTM D 3398
Particle shape will affect the density and workability of concrete (CRD-C 129).
Soundness of
aggregate in concrete
CRD-C 114
(ASTM C 666)
Results are directly related to the F/T resistance of concrete.
Frost resistance ASTM C 682 This test may be valuable in evaluating frost resistance of coarse aggregate in concrete
(CRD-C 115).
Abrasion loss ASTM C 131
ASTM C 535
These tests may indicate the degree of resistance to degrading of coarse aggregates
during handling and mixing (CRD-C 117 and 145, respectively).
Specific heat CRD-C 124 Needed for thermal analysis.
Linear thermal
expansion
CRD-C 125
CRD-C 126
Needed for thermal analysis. Aggregates with very high or low thermal coefficient may
require further investigation.
Alkali-silica reactivity ASTM C 289
ASTM C 227
Perform these tests if there is an indication of potential alkali-silica reactivity (CRD-C 128
and 123, respectively). (See Appendix D for details.)
Alkali-carbonate
reactivity
ASTM C 586 Perform this test if there is an indication of potential alkali-carbonate reactivity (CRD-C
146). (See Appendix E for details.)
Concrete making
properties
ASTM C 39
and others
Perform these tests as needed to determine the suitability of aggregates for high strength
concrete (CRD-C 14).
*Test methods cited are from the American Society for Testing and Materials Annual Book of ASTM Standards (ASTM
Annual) and from Department of the Army, Corps of Engineers, Handbook of Concrete and Cement (USAEWES 1949).
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25. EM 111 o-2-2000
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(f) Soft constituents, clay lumps, and lightweight
particles (ASTM C 123 (CRD-C 122); ASTM C 851(CRD-
C 130); CRD-C 141; ASTM C 142 (CRD-C 142)). Results
of tests for soft particles, clay lumps, and lightweight
pieces are largely used as information that may have a
bearing on or assist in rationalizing results of other tests
such as the accelerated weathering test or the strength
properties of the concrete. The tests may sometimes be
useful in determining whether or not processing of the
material to remove the undesirable constituents is
feasible when they occur in proportions which make the
material unfit for use without removal.
(g) Particle shape (ASTM D 4791; CRD-C 120; ASTM
D 3398 (CRD-C 129)). The test for flat and elongated
particles provides information on particle shape of
aggregates. Excessive amounts of flat or elongated
particles, or both, in aggregates will severely affect the
water demand and finishability. In mass concrete
structures, the amount of flat or elongated particles, or
both, at a 3:l length-to-width (L/W) or width-to-
thickness (W/T) ratio is limited to 25 percent in any size
group of coarse aggregate. Although there is no
requirement in structural concrete, the effect of more
than 25 percent flat or elongated particles should be
examined during the design process. The results of the
examination should be discussed in the appropriate
design memorandum. The maximum L/W or W/T
ratio, when testing in accordance with ASTM D 4791 is
normally 3:l.
(h) Soundness of aggregate by freezing and thawing
in concrete (CRD-C 114). This test is similar to ASTM C
666 (CRD-C 20), procedure A, except that a standard
concrete mixture is used to evaluate the effect of
aggregates on freezing-and-thawing resistance. This test
is more severe than the aggregates will experience in
service. Nevertheless, it provides an important
measurement in relative aggregate quality in freezing-
and-thawing resistance and is the best means now
available for judging the relative effect of aggregates on
frost resistance. In general, however, aggregates are
rated in relative quality by this test as shown in Table 2-
4. This table also provides the recommended DFE value based
upon the project location, and expected exposure. For the
purpose of simplicity the weathering region (Fig. I) in ASTM
C 33 is used as an indicator of the potential freeze and thaw
exposure for the area. The engineer may adjust this
requirement if there is data available indicating that the
situation is different from the one shown in ASTM C 33 Fig. 1.
Although the test is reasonably repeatable, it is not
possible to prevent small differences in the size and
distribution of air voids caused by different cements and
air-entraining admixtures and possible other factors;
thus, it is not possible to judge accurately the quality of
protection of cement paste in each instance even though
air content for all tests is kept within a small range.
Therefore, it is not unusual to find that these differences
will cause variations in test results of sufficient
magnitude from two separate tests on essentially
identical aggregate samples to shift the quality rating
from one level to another. The test also has limitations
on the size of aggregates that can be tested. The
maximum size of aggregate used in the tests is l% 19.0
mm (3/4 in.), whereas aggregate up to 150 mm (6 in.) is
frequently used in mass concrete. Therefore, the test is of
limited value when the +19.0-mm (+3/4in.) aggregate
varies substantially in characteristics from that finer than
19.0 mm (3/4 in.). In spite of its limitations, the test
provides an excellent means of evaluating the relative
quality of most materials and results of the test should
be given prime consideration in selecting aggregate
quality requirements. Where the laboratory freezing-
and-thawing test is considered inadequate as a basis for
judging the quality of the aggregates, particularly for
sizes larger than 19.0 mm (3/4 in.), concrete made with
the larger sizes may be exposed at Treat Island, Maine,
where the Corps of Engineers’ severe-weathering
exposure station is located to determine the durability of
the specimens. The decision to expose specimens at
Treat Island should be made early in the investigation so
that they may be exposed for at least two winters. To
determine durability, 2-ft cube specimens cast from air-
entrained concrete containing the desired maximum size
of aggregate should be used. In an average period of 2
years, specimens are subjected to at least 250 cycles of
freezing and thawing. If no marked reduction in pulse
velocity has occurred and no distress is visually evident
in the period, the aggregates may be considered to be of
good to excellent quality.
(i) Frost-resistance test (ASTM C 682 (CRD-C 115)).
This dilation test provides another indication of
aggregate quality in freezing-and-thawing resistance
when used in concrete. It measures the dilation of a
specimen under slow freezing-and-thawing cycles and is
similar to ASTM C 671 (CRD-C 40) except a standard air-
entrained concrete mixture is used. In air-entrained
concrete in which the paste is adequately protected
against frost action, the quality of the aggregate is the
main factor that contributes to deterioration. Results of
this test are very sensitive to the moisture condition of
aggregate and concrete and should be compared
carefully with the conditions in the field.
(j) Sulfate soundness (ASTM C 88 (CRD-c 137)). In
the past, ASTM C 88, “Soundness of Aggregates by Use
of Sodium Sulfate or Magnesium Sulfate,” has been used
quite often. This test is the only one which is performed
on aggregate directly by soaking material in sulfate
solution to simulate the effect of increase in volume of
water changing to ice or freezing in the aggregate pores.
ASTM C 88 is not recommended due to its poor
correlation with the actual service performance of
concrete.
(k) Abrasion loss (ASTM C 131 (CRD-C 117); ASTM
C 535 (CRD-C 145)). If a material performs well in other
tests, particularly resistance to freezing and thawing, high
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26. EM 1110-2-2000
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Change 2
Table 2-4
Concrete Durability Factors for Assessing Aggregate Durability.
DFE Range* Over 75 50-75 25-50 Less than 25
Region per
ASTM C33
Fig. I
Severe Moderate Negligible No F/T cycle
I L
Quality Rating Excellent Good Fair Poor
*DFE = Durability factor (based on relative dynamic modulus of elasticity).
abrasion loss may not be significant. It should be recognized,
however, that a material having high abrasion loss will tend to
degrade in handling and that excessive grinding may occur with
such materials during mixing. These aspects should be
investigated as a basis for evaluating the acceptability of a
material. It should be noted that there is no relationship between
abrasion loss from these tests and concrete abrasion or durability
in service.
(1) Specific heat and thermal expansion (CRD-C 124,
CRD-C 125, CRD-C 126). The results of these tests are
properties of the aggregate and are needed when performing
thermal analysis.
(m) Alkali-aggregate reactivity (ASTM C 227; ASTM C
289; ASTM C 586 (CRD-C 123, 128, and 146, respectively)).
Criteria for recognizing potentially deleterious constituents in
aggregate and for evaluating potential alkali-silica and alkali-
carbonate reactivity are given in Appendixes D and E,
respectively. If aggregates containing reactive constituents are to
be used, the problem then becomes one of identifying the
reactive constituents and determining the conditions under
which the available aggregates may be used. Where the reactive
constituents can be positively determined to occur in such small
proportions as to be innocuous, an aggregate, if otherwise of
suitable quality, may be used without special precautions. Where
the reactive constituents occur in such proportions that they are
potentially deleteriously reactive, it will be necessary to use low-
alkali cement or an effective pozzolan, or both, with the
aggregate. If the requirement of low-alkali cement would impose
serious difficulties of cement procurement or excessive increase
in cost, consideration should be given to the use of portland
blast-furnace slag cement (a blend of portland cement and slag),
Portland-pozzolan cement, cement with GGBF slag, or cement
with a pozzolan, or both, that will prevent excessive reaction
even when high alkali-cement is used. When consideration is
given to the use of any of these materials in lieu of low-alkali
cement, mortar-bar tests should be conducted to verify that the
potentially deleterious expansion will be reduced to meet the
criteria in Appendix D or E. If petrographic examination
determines the presence of potentially reactive materials in
excess of the limits given in Appendix D, mortar-bar tests,
ASTM C 227 shall be performed. If the petrographic
examination determines the presence of strained quartz in excess
of the limit given in Appendix D, the high- temperature mortar-
bar test shall be performed.
(n) Concrete making properties (ASTM C 39 (CRD-C
14)). When it is desired to select aggregate for concrete with
strengths of 6,000 psi or greater, some otherwise acceptable
aggregates may not be suitable. Concrete-strength specimens,
made from concrete using the aggregate being evaluated and of
the required slump and air contents, should be tested at various
cement factors, w/c, and including any required chemical
admixtures. If the required strength cannot be obtained with a
reasonable slump, air content, cement factor, and chemical
admixture(s), the aggregate should not be considered as
acceptable for the high strength concrete. Materials that are
satisfactory in other respects usually have acceptable strength
and bonding characteristics. A complete discussion of high-
strength concrete may be found in AC1 363R.
(0) Service performance. The performance of aggregates
in service in structures is considered the best general evidence of
aggregate quality when dependable records are available and the
exposure conditions are similar. Service records are usually of
greater usefulness when commercial sources of aggregate are
being investigated. Service performance, however, must be
considered with caution. Poor condition of a structure is not
necessarily evidence of poor quality aggregate. There are many
factors which may contribute to the poor performance of the
concrete in service. However, except where a slow acting
reactive aggregate is involved, a structure in good condition is
always an indication that the aggregates are of adequate quality
for concrete exposed to similar conditions.
(7) Nominal maximum size aggregate. In general, it is
economical to use the largest aggregate compatible with placing
conditions. Table 2-5 provides guidance in making the
selection. On projects not involving large quantities of
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27. EM 1110-2-2000
1 Feb 94
Table 2-5
Nominal Maximum Size of Aggregate Recommended for
Various Types of Construction
Features Nominal Maximum Sizes
Section 7-1/2 in. or less in width or slabs 4 in. or less in
thickness. Heavily reinforced floor and roof slabs. Parapets,
corbels, and all sections where space is limited and surface
appearance is important.
High-strength concrete
19.0 mm (3/4 in.)
Section 7-1/2 in. wide and in which the clear distance
between reinforcement bars is at least 2-1/4 in. and slabs at
least 4 in. thick.
37.5 mm (1-1/2 in.)
Unreinforced sections over 12 in. wide and reinforced
sections over 18 in. wide, in which the clear distance
between reinforcement bars is over 4-1/2 in. Piers, walls,
baffles, and stilling basin floor slabs in which satisfactory
placement of 6-in. aggregate concrete cannot be
accomplished even though reinforcement spacing would
permit the use of large aggregate. Slabs 10 in. or greater in
thickness.
75 mm (3 in.)
Massive sections of dams and retaining walls; ogee crests,
piers, walls, and baffles in which clear distance between
reinforcement bars is at least 9 in. and for which suitable
provision is made for placing concrete containing the large
sizes of aggregate without producing rock pockets or other
undesirable results. Slabs 24 in. or greater in thickness.
150 mm (6 in.)
concrete, a careful study should be made of the economy of
large aggregates. The use of large aggregates reduces the
cement content, but it increases plant costs because
provision must be made for the handling of more individual
sizes. Nominal maximum size aggregate (NMSA), 150 mm
(6 in.) or even 75 mm (3 in.), should not be specified if the
volume of concrete is so small that savings in cement will
not pay for increased plant expenses. When an economic
study indicates the use of 75-mm (3-in.) or 150-mm (6-in.)
NMSA concrete results in comparable costs and the
additional cement required in the 75-mm (3-in.) NMSA
concrete does not detrimentally affect the concrete, optional
bidding schedules should be used. The additional
cementitious quantities of 40 lb/cu yd of concrete is typical
when 75-mm (3-in.) NMSA concrete is used in lieu of
150-mm (6-in.) NMSA concrete.
(8) Fine aggregate grading requirements. During the
course of the aggregate investigations, the grading of the
available fine aggregate from all sources should be
determined and compared to the anticipated project
specifications. The project grading requirements will
depend on the guide specification selected for the project.
If the most readily available materials do not meet the
applicable grading requirements and the processing required
to bring the material into the specified grading limits results
in increased costs, consideration should be given to
substituting a state or local specification that is determined
to cover the fine aggregate grading available at commercial
sources in the project area. The substitution should be
based on the determination that concrete meeting the project
requirements can be produced using the locally available
fine aggregate. If a large mass concrete structure is
involved which will be built to the requirements of
CW-03305, "Guide Specification for Mass Concrete," using
an onsite fine aggregate source, the decision to waive the
grading requirements will also be based on the results of the
processibility study, which includes estimates of waste and
laboratory data that show that concrete can be produced
using the fine aggregate grading proposed which meets all
the project requirements. The study should include an
economic evaluation which shows, clearly, that the increased
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28. EM 1110-2-2000
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cost of cement and finishing, when a nonstandard grading is
used, will be more than offset by the savings in processing
and waste reduction. Particular attention should be given to
the increased workability gained by use of an optimum
amount of material finer than the 300-µm (No. 50) and
150 µm (No. 100) sieves. Many studies have shown that it
is cost effective to blend in a fine "admix" sand in this size
range if the available sand is deficient in these sizes. The
limits to be permitted on the proposed grading should also
be stated. Manufactured fine aggregate has a tendency for
the dust that is generated during the crushing and sizing
process to cling to the larger particles and to clump or ball
up when exposed to moisture. The amount of dust can be
significant and can cause problems during construction. The
dust may not come loose or break up during sieving per
ASTM C 136 (dry grading), and it may be difficult to
accurately monitor the grading. The dust can also cause the
moisture content of stockpiled material to be higher and
more variable than expected; this in turn can result in
difficulties controlling the batch masses and slump of the
concrete. Excessive dust can cause the water demand of
concrete to increase with resultant loss of strength.
Therefore, when manufactured sand is allowed in project
specifications, the designer should invoke the optional
requirements in CW 03305, "Guide Specification for Mass
Concrete," that will limit the amount of material (dust)
passing the 75-µm (No. 200) sieve and that will require
washing the material during grading testing (ASTM C 117
(CRD-C 105)). The option may also be invoked for natural
fine aggregate at the designer’s discretion.
(9) Required tests and test limits.
(a) General. For all civil works concrete construction
projects except those for which the guide specification
CW-03307, "Concrete for Minor Structures," is used, a list
of required quality tests and test limits must be established
and inserted in the specifications. Required tests and test
limits must be site-specific for the project area, the general
rule being that the best locally available aggregates are to be
used. This list of tests and test limits may be specific for
only one project or, according to the amount of diversity of
the geology and the resulting rock types in an area, could be
district- or division-wide lists. On some projects where, for
instance, both river gravels and crushed stone are included
in the list of sources, a set of tests and test limits would be
required for the gravel and a slightly different set of tests
and test limits would be required for the crushed stone.
(b) Acceptance criteria. Establishing test limits for
aggregate quality for a project is very complex and should
be done with great care and deliberation. Limits established
for a specific test for one rock type at one project would not
necessarily assure durable concrete for a different rock type
at the same project or for the same rock type at a different
project. For example, a minimum density of 2.52 for coarse
aggregate at a specific project may be adequate for some
types of chert or river gravel but would not be adequate for
crushed limestone. The selection of which tests to specify
for indicating the quality of aggregate and the respective
acceptance limits for each test should come after completion
of all testing for each source or formation and should
include due consideration of service records. The
acceptance limits should be set recognizing that all test
results have some scatter and that most ASTM (CRD) test
methods include precision and bias statements.
EM 1110-2-2302, "Construction with Large Stone," contains
an excellent discussion on setting acceptance criteria and
should be consulted for further guidance. The district
materials engineer should work closely with the division
office when establishing acceptance criteria for a project so
that close coordination between adjacent districts and
between adjacent divisions can be maintained for a given
source or formation.
(10) Aggregate processing study. A processing study
should be considered for any government-furnished source.
The processing study should be conducted by a division
laboratory having the capability of processing large (1- to 2-
ton) samples. The sample should be processed to meet the
grading and particle-shape requirements of the project by
crushing and screening as necessary. The processing study
will provide information on which to base estimates of
waste and also will provide an indication of the potential for
the development of flat and elongated particles to an extent
which will influence the workability and cement
requirements of the concrete. For large mass concrete jobs,
a test quarry may be required. This is usually done as a
separate construction contract to qualified private companies
skilled in blasting (if a quarry operation) and skilled in
processing rock or gravel deposits to meet concrete
aggregate gradings. In this more elaborate type of
investigation, the processing of the raw material would be
accomplished onsite, instead of in the division laboratory.
Information to be required would include optimum blasting
patterns, quality of each rock stratum, amount of waste,
particle shape, and the ability of the deposit to be processed
into the required gradings.
(11) Location of government-furnished quarry or pit.
The objective should be to define clearly one or more areas
which will be described in the specifications and shown in
the contract drawings. The purpose will be to provide the
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29. EM 1110-2-2000
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bidders with information that will make it possible for them
to estimate accurately the cost of producing the aggregate
and subsequently to provide information to the contractor
for use in planning his aggregate production operations.
Explorations should be carefully logged and the information
included in the contract drawings. Materials recovered
during these and previous explorations should be preserved
and made available for inspection by the bidders and by the
Contractor for use in planning his work. Where zones or
layers exist that are unsuitable, they should be specifically
identified and the listing of the source should note the
unsuitability of those zones or layers.
2-4. Water for Mixing and Curing
a. General. The most readily available water
sources at the project site should be investigated during the
PED phase for suitability for mixing and curing water.
Also, water that will be in contact with the completed
structure should be tested to determine if it contains a
concentration of chemicals which may attack the hardened
concrete. For additional information, see the Portland
Cement Association’s "Design and Control of Concrete
Mixtures" (Kosmatka and Panarese 1988).
b. Mixing water. To determine if water from sources
other than a municipal water supply is suitable for mixing,
it should be investigated during the PED phase in
accordance with CRD-C 400 (USAEWES 1949). If
contamination by silt or a deleterious material exists,
samples should be taken when contamination is the greatest.
c. Curing water. Water for curing must not contain
harmful chemical concentrations and it must not contain
organic materials such as tannic acid or iron compounds
which will cause staining. If certain water sources around
the project area have a potential for staining and others are
nonstaining, the staining sources should be eliminated from
use by the specifications and the acceptable sources noted
so that unsightly staining may be prevented. However, the
Contractor is responsible for providing surfaces free of stain
after curing. This is a preferable approach to attempting to
remove the staining with often unsatisfactory results.
Curing water should be tested in accordance with
CRD-C 400.
2-5. Chemical Admixtures
a. General. The chemical admixtures that may be used
in concrete on Corps projects are air-entraining admixtures
(ASTM C 260), accelerating admixtures, water-reducing
admixtures, retarding admixtures, water-reducing and
retarding admixtures, water-reducing and accelerating
admixtures, high-range water-reducing admixtures, and high-
range water-reducing and retarding admixtures. All of the
latter are discussed in ASTM C 494 (CRD-C 87). Chemical
admixtures to produce flowing concrete are discussed in
ASTM C 1017 (CRD-C 88). Other admixtures may be used
when their use on the project results in improved quality or
economy. When admixtures are considered during the PED
phase to provide special concrete properties, trial batches
with materials representative of those that will be used for
the project should be proportioned and tested. The effects
of the admixture on the concrete properties and the required
dosage rate should be reported in the concrete materials
DM. Admixtures proposed for use during construction
should be checked with trial batches, using the actual project
materials in the Division laboratory. However, if the source
of the concrete is a ready-mix plant with a recent history of
use of the admixture with project materials, trial batches
need not be required. In some instances, adverse reactions
may occur between admixtures or between admixtures and
cement or water. Admixtures should not be mixed together
prior to batching, but each should be batched separately. A
detailed discussion of chemical admixtures for concrete is
given in ACI 212.3R.
b. Air-entraining admixtures. Air-entraining admixtures
(AEA’s) are organic materials which entrain small air
bubbles into concrete. These bubbles become a part of the
cement paste that binds the aggregates together in the
hardened concrete. Air entrainment improves the
workability of concrete, reduces bleeding and segregation,
and most importantly improves the frost resistance of
concrete. Air entrainment is essential to ensure the
durability of concrete that will become critically saturated
with water and then exposed to freezing-and-thawing
conditions. However, air entrainment only protects the paste
fraction of the concrete. It does not protect concrete from
deterioration caused by nonfrost-resistant aggregates.
(1) Policy. All civil works concrete should be air
entrained with an appropriate AEA. Any exceptions to this
practice must be submitted to CECW-EG for approval.
(2) Strength loss. Even if freezing-and-thawing
conditions are not prevalent, concrete should be air entrained
because of the benefits imparted in other ways. The
presence of entrained air results in an improvement in the
workability of concrete at the same water content. To
maintain a given slump, a reduction in the water content of
up to 15 percent can be made depending upon the air and
cement contents. The reduction in the water content results
in a lower w/c, which will offset some or all of the loss in
strength due to the presence of the entrained air, depending
on the cement content; calculations indicate that at about
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30. EM 1110-2-2000
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300 lb of cement per cubic yard, an increase in air content
will be balanced by a sufficient decrease in w/c at constant
slump to maintain constant strength.
(3) Bleeding. Air-entrained concrete is less susceptible
to bleeding. When successive lifts of concrete are to be
placed, more effort will be required for horizontal lift joint
cleanup if bleeding is excessive. A considerable reduction
in bleeding by proper air entrainment is usually a major
benefit. Air entrainment also imparts a buoyant action to
the cement and aggregate particles which helps to prevent
segregation. Even though it is an aid against segregation, it
cannot prevent segregation of concretes having poorly
graded aggregates, ones that are excessively lean or wet, or
ones that are improperly transported or placed.
(4) Batching AEA. An AEA should be added to the
mixing water prior to its introduction into other concrete
materials. If other admixtures are also used, the AEA
should be added to the concrete mixer separately and not
intermixed with the other admixtures.
(5) Dosage. Many variables will determine the exact
dosage of an AEA needed to achieve the proper air-void
system in a concrete mixture. In general, larger amounts of
AEA will produce higher air contents in a concrete mixture.
However, there is no direct relationship between the dosage
rate of a given AEA and the air content that is produced.
(6) Effects of water content on air content. Air content
will usually increase or decrease as the water content of a
mixture is increased or decreased. An increase in the water
content in the concrete results in a more fluid mixture into
which the air bubbles can be more easily incorporated by
the mixing action. For example, a slump increase of about
3 in. can cause an increase in air content of about 1 percent
with the same dosage of an AEA.
(7) Effects of fine aggregate grading on air content.
Air is more easily entrained in concretes having higher
percentages of fine aggregate. The fine aggregates provide
interstices that can contain the air bubbles, especially the
sizes from about 600 µm (No. 30) to the 150 µm (No. 100).
Concretes made with fine aggregates deficient in particles of
these sizes can require larger amounts of AEA’s to achieve
the desired air content, especially in lean concretes.
Conversely, concretes made with an excess of finely divided
materials can also require larger amounts of AEA’s to
achieve the desired air content. Very fine sand fractions
(150 µm (No. 100) and smaller), fly ash , and high cement
contents have caused a reduction in air contents. Fly ashes
which have high loss on ignition cause an especially large
reduction in the air content. Concrete made with a Type III
cement can require up to 50 percent more AEA’s than
concrete made with a Type I cement.
(8) Effects of temperature on air content. The
temperature of the concrete has a direct effect upon the air
content of the concrete at given AEA dosage. A lower
temperature results in a higher air content, and vice versa.
Therefore, if the concrete temperature changes significantly
during production of a particular concrete mixture, it is
likely that the amount of AEA must be adjusted accordingly
to maintain the desired air content.
(9) Effect of other admixtures on air content. Less
AEA is generally required to entrain air in concrete when
water-reducing or retarding admixtures are also used. The
required amount of AEA may be as much as 50 percent
less, especially when lignosulfonate-based chemical
admixtures are used because these materials also have a
moderate air-entraining capacity.
(10) Effect of mixing action on air content. Effective
mixing action is necessary to produce air-entrained concrete.
The amount of entrained air will vary with the type and
physical condition of the mixer, the mixing speed, and the
amount of concrete being mixed. It is more difficult to
entrain air in concrete using a severely worn mixer or one
that has an excessive amount of hardened concrete buildup
on the blades or in the drum. Air contents can also
decrease if the mixer is loaded above its rated capacity.
Studies have shown that air contents generally increase with
mixing up to about 15 min. Thereafter, additional mixing
leads to a decrease in air content, especially for low-slump
concretes. Any transporting technique that will continue to
agitate the concrete, such as pumping or conveying, usually
decreases the air content.
c. Accelerating admixture. Accelerating admixtures
are classified by ASTM C 494 as Type C, accelerating, or
Type E, water-reducing and accelerating. Accelerating
admixtures accelerate the setting time or early strength
development of concrete or both. Initial and final setting
times must be accelerated by a minimum of 1 hr, and 3-day
compressive strengths must be increased by a minimum of
25 percent in order for an accelerating admixture to comply
with the requirements of ASTM C 494 (CRD-C 87).
(1) Uses. CW-03301 and CW-03305 provide for the
use of nonchloride accelerating admixtures subject to the
approval of the Contracting officer. The use of a
nonchloride accelerating admixture may be approved when
concrete is being placed in cold weather to partially offset
the retarding effect of the lower temperatures. Its use
permits earlier finishing of slabs and reduces form removal
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31. EM 1110-2-2000
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delays. The use of an accelerating admixture does not
permit a reduction of specified curing and protection
periods.
(2) Nonchloride admixtures. Several nonchloride
organic and inorganic compounds, such as calcium formate,
calcium nitrite, and triethanolamine, are available as
accelerators. However, experience and published research
on these admixtures are limited. The available data suggest
that none of the nonchloride accelerating admixtures are as
powerful an accelerator as calcium chloride at equal
dosages. However, adequate acceleration can usually be
attained with a nonchloride accelerating admixture if the
proper dosage is used. Nonchloride accelerators usually
come in liquid form and should be added at the mixer with
a portion of the mixing water at a dosage rate recommended
by the manufacturer. They should be added to the concrete
separately and not mixed with other admixtures. In some
instances, adverse reactions occur between admixtures which
can decrease their effectiveness.
(3) Effect on fresh concrete properties. Type C
accelerating admixtures have no significant effect on the
initial workability or air content of a concrete mixture;
however, the setting time, heat evolution, and strength
development are affected. Concretes containing an
accelerating admixture can have a more rapid slump loss,
especially concretes having a high cement content. The
bleeding of a concrete mixture is generally reduced when an
accelerating admixture is used.
(4) Effect on hardened concrete properties. Properties
of hardened concretes containing an accelerating admixture
are generally increased at early ages but may be decreased
at later ages. Compressive and flexural strengths will be
higher at early ages but can be lower than those of plain
concrete at later ages. Both creep and drying shrinkage may
increase. Concretes containing accelerators may be less
resistant to aggressive environments, especially at later ages.
The passive layer of protection at the concrete-steel interface
does not appear to be attacked by nonchloride accelerators.
Proper curing procedures are essential when concrete
contains an accelerating admixture.
(5) Other methods of accelerating strength
development. Frequently, the acceleration of setting time
and early strength development can be obtained by other
means, such as (a) using a Type III portland cement, (b)
using additional cement, (c) lowering the pozzolan content,
(d) warming water and aggregates, (e) improving curing and
protection, or (f) some combination of these. In some cases,
the use of an accelerator is the most convenient and
economical method of achieving the desired results;
however, convenience and economics should not take
precedence over durability considerations.
d. Retarding admixtures. Retarding admixtures are
materials which cause a delay in initial and final setting
times. However, retarding admixtures do not reduce the rate
of slump loss. Retarding admixtures are classified by
ASTM C 494 (CRD-C 87) as Type B, retarding, or Type D,
water-reducing and retarding. They must retard the initial
setting time by a minimum of 1 hr and the final setting time
by a minimum of 3-1/2 hr. Setting times of concrete made
with a portland cement-pozzolan blend will typically be
retarded more than when portland cement alone is used.
The pozzolan often has a retarding action.
(1) General uses. By using the proper dosage of a
retarding admixture, the setting time of a mixture can be
extended so as to avoid cold joints and allow for proper
finishing. A change in temperature could require an
adjustment in the dosage of retarder to maintain the desired
setting time. Retarding admixtures can be beneficial in hot
weather, when long hauling distances are unavoidable, or
anytime extended working times are desirable. The time
between screeding and troweling operations of concrete
slabs is extended when retarding admixtures are used. This
can be particularly beneficial in hot weather; however,
unless proper precautions are taken, such as the use of
sunscreens and wind screens, the surface may dry
prematurely and create a crust on the surface. Under these
conditions, careful attention to curing and protection is
required to obtain a uniform hardening in the entire concrete
slab. Retarding admixtures based on hydroxylated
carboxylic acids and their salts are beneficial in concrete
used in flatwork construction during hot weather since they
induce bleeding and, therefore, aid in the prevention of a
premature drying of the top surface.
(2) Dosage. The dosage of admixture recommended by
the manufacturer should be used unless experience or results
of trial batches indicate otherwise. High temperatures may
require higher dosages of retarding admixtures; however,
overdosage can cause excessive retardation requiring longer
curing times and delays in form removal. The degree of
excessive retardation could be from a few hours to a few
days. However, an accidental overdosage of a retarding
admixture does not adversely affect the later age properties
of a concrete if the concrete is cured properly and the forms
are not removed until sufficient strength has been attained.
Research has shown that a higher dosage of retarding
admixtures is needed when used with portland cements that
have high C3A and C3S contents, as well as a high alkali
content. Therefore, to achieve the same effects, a larger
dosage of retarding admixture will probably be required if
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32. EM 1110-2-2000
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a Type I portland cement is used than will be required if a
Type II, low-alkali portland cement is used.
(3) Batching. Retarding admixtures should be added to
the mixing water prior to its introduction into other concrete
materials. If other admixtures are also used, the retarding
admixture should be added to the concrete mixture
separately and not mixed with the other admixtures. In
some instances, adverse reactions occur between admixtures
which can decrease their effectiveness.
(4) Effect on strength. When retarding admixtures are
used in concrete, early-age compressive and flexural
strength may be reduced. If a low dosage of admixture is
used, the lower strengths may be evident for as few as 1 or
2 days. Greater degrees of retardation may cause the
strengths to be lower for 3 to 7 days. However, in most
cases there will be no retardation of strength development
by 28-days age. Lower strengths may exist for a longer
period of time if the concrete is made with a portland
cement-pozzolan blend. At later ages, the strength of
concrete made with a retarding admixture will usually be
higher than that of concrete containing no retarding
admixture.
e. Water-reducing admixtures. Water-reducing
admixtures (WRA’s) are organic materials which reduce the
amount of mixing water required to impart a given
workability to concrete. By definition, WRA’s are required
to provide a water reduction of at least 5 percent and are
classified by ASTM C 494 (CRD-C 87) as Type A, water-
reducing; Type D, water-reducing and retarding; or Type E,
water-reducing and accelerating. They can be used to
increase strength, increase workability, or reduce the cement
content of a concrete mixture.
(1) Use in mass concrete. A WRA generally should
not be allowed in lean mass concrete mixtures since neither
high strength nor high slump are usually required from these
mixtures. A reduction in the cement content permitted by
the use of a WRA could result in the mixture having
inadequate workability. This is especially true for mass
concrete mixtures containing 37.5-mm (1-1/2-in.) or larger
nominal maximum size aggregate.
(2) Dosage. The usual dosage rate for a WRA is
between about 2 and 8 fl oz/100 lb of cementitious material.
The appropriate amount will be determined by the brand of
WRA being used as well as the combination of other
concrete materials. Some WRA’s meet ASTM C 494
(CRD-C 87) requirements for both Type A and Type D,
depending upon the dosage rate used. These WRA’s will
usually react as a Type A at the lower limit of the
recommended dosage range and as a Type D at the upper
limit of the recommended dosage range.
(3) Use in hot or cool weather. A Type D WRA can
be beneficial when working in hot weather, when long
hauling times are involved, or anytime extended working
times are desirable. However, the retarding effect increases
the concrete setting time only. It does not slow the rate of
slump loss. In fact, concretes containing either Type A,
Type D, or Type E WRA generally lose slump at a faster
rate than when a WRA is not used. A Type E WRA may
be beneficial when working in cool temperatures or when
higher earlier strengths are desired.
(4) Air entrainment. Most lignosulfonate WRA’s will
entrain air. However, the amount of entrained air will
usually not be sufficient to provide adequate frost resistance.
An AEA will be required in addition to the WRA, but the
amount of AEA necessary may be as much as 50 percent
less. WRA’s based on other compounds generally do not
entrain air but do enhance the air-entraining capability of
AEA’s.
(5) Bleeding. WRA’s affect the rate and capacity of
fresh concrete to bleed. Lignosulfonate WRA’s reduce the
bleeding rate and capacity while WRA’s based on
hydroxylated carboxylic acids and their salts increase the
bleeding rate and capacity of a concrete mixture. A
lignosulfonate WRA should be used with caution in concrete
placed in slabs during hot weather. With little bleed water
migrating to the surface, rapid surface drying could occur,
leading to a crust on the concrete surface while the concrete
underneath remains plastic. The potential for plastic
shrinkage cracking is also greater. It is beneficial to induce
bleeding under these ambient conditions. WRA’s based on
hydroxylated carboxylic acids and their salts will accomplish
this objective.
f. High-range water-reducing admixtures
("superplasticizers"). High-range water-reducing admixtures
(HRWRA’s) are chemically different from normal WRA’s
and are capable of reducing water contents by as much as
30 percent without detrimentally affecting air content,
bleeding, segregation, setting time, and hardened properties.
By definition, HRWRA’s are required to provide a water
reduction of at least 12 percent and are classified by ASTM
C 494 as Type F, high-range water-reducing, or Type G,
high-range water-reducing and retarding. HRWRA’s can be
used to produce concrete having high workability for easy
placement, high strength with normal workability, or
combinations of the two. HRWRA’s can also be used to
produce flowing concrete as described by ASTM C 1017
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33. EM 1110-2-2000
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(CRD-C 88). Additional information on flowing concrete
may be found in paragraph 10-9.
(1) Effect on workability. Significantly higher
compressive strengths are possible with the use of an
HRWRA. Concrete can be produced having a lower w/c
without the loss of workability that could occur with the use
of WRA’s. The increased workability made possible with
an HRWRA permits easier placement of concrete in
congested reinforcement and in areas where access is
limited. HRWRA’s are beneficial in concrete which is
pumped or placed by tremie because they improve
workability without a loss in cohesiveness. The dispersing
action of HRWRA is effective on both portland cements and
pozzolans. The ability of an HRWRA to increase the slump
of concrete depends upon the chemical nature of the
HRWRA, the dosage used, time of addition, initial slump,
composition and amount of cement, and concrete
temperature. Recommended dosages of HRWRA’s are
usually greater than those of WRA’s. There are some
limitations of HRWRA’s that should be recognized. Under
some conditions, concretes containing HRWRA’s may
exhibit a rapid slump loss as soon as 30 min after
completion of mixing. Therefore, HRWRA’s are often
added to truck mixers at the job site to minimize placing
and consolidation problems associated with concrete which
stiffens rapidly.
(2) Effect on segregation and bleeding. When
HRWRA’s are used as water reducers, bleeding of the
concrete is usually reduced. Segregation of the aggregates
will not be a problem. When HRWRA’s are used to
produce flowing concrete, both bleeding and segregation can
occur if precautions are not taken. Increasing the volume of
sand in the mixture by 3 to 5 percent may be necessary.
The dosage of HRWRA should be limited to the minimum
amount necessary to produce the desired slump. An
overdose can cause excessive bleeding and segregation.
However, bleeding and segregation of a high-slump concrete
is not as pronounced when the high slump is achieved
through use of an HRWRA as would be the case if the high
slump were achieved through the addition of extra water.
Retempering once with an HRWRA is generally an
acceptable practice.
(3) Effect on air entrainment. Some HRWRA’s
enhance the air-entraining capability of AEA’s. However,
HRWRA’s can also facilitate the escape of air. Repeated
dosing with an HRWRA can accentuate this effect. In
addition to the rapid slump loss, a significant loss of air can
occur.
(4) Effect on setting time. A Type F HRWRA has
little effect upon setting times of concrete, while a Type G
HRWRA retards the setting time. The usual dosage range
for HRWRA is between about 10 and 30 fl oz/100 lb of
cementitious materials. The appropriate amount will be
determined by the type of HRWRA being used as well as
the combination of other concrete materials and admixtures.
Some HRWRA’s meet ASTM C 494 requirements for both
Type F and Type G, depending on the dosage rate used.
These HRWRA’s will usually react as a Type F at the lower
end of the recommended dosage range and as a Type G at
the upper end of the recommended dosage range. If one of
these HRWRA’s is being used at a low dosage, and it is
desired to increase the dosage for additional water reduction,
caution should be exercised. The higher dosage could cause
undesirable retardation of concrete setting time and strength.
(5) Compatibility with other admixtures. HRWRA’s
are generally compatible with most other concrete
admixtures. However, each admixture combination should
be evaluated prior to being used. In particular, attention
should be given to the air content and air-void system
parameters. Appropriate durability tests should be
performed depending on the environment to which the
concrete will be subjected. When concrete containing an
HRWRA is properly air entrained, it will be as durable as
that without an HRWRA.
g. Antiwashout admixtures. In recent years a group of
chemical admixtures known as antiwashout admixtures
(AWA’s) has been introduced into the concrete products
market. ASTM standard specifications have not yet been
developed for these admixtures. They are used to increase
the cohesiveness of a concrete to prevent excessive washing
out of cementitious materials when the concrete is placed
underwater. A workability transformation occurs after
several minutes of mixing, thereby causing the concrete to
become very sticky. Present guide specifications do not
include AWA’s. The use of AWA’s should be discussed in
the appropriate DM.
(1) General. AWA’s can be made from various
organic and inorganic materials. The two materials most
commonly marketed as AWA’s are cellulose and gum.
They act primarily by increasing the viscosity and the water
retention of the cement paste. Both materials are very
effective in increasing the washout resistance of a concrete
mixture. The washout resistance depends upon the type and
dosage of AWA, w/c, cement content, and other admixtures
used. In general, the washout resistance increases with an
increase of AWA, a decrease in w/c, and an increase in
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34. EM 1110-2-2000
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cement content. The loss of cementitious materials due to
washing is typically reduced by as much as 50 percent when
concrete contains an AWA.
(2) Batching. AWA’s based on cellulose are normally
packaged in a powder form. They are usually added to the
concrete mixer with the cement. AWA’s based on gum
may be packaged either as a powder or liquid. The powder
should be put into solution with a portion of the mixing
water prior to introduction into the concrete mixture. The
liquid can be added with the mixing water.
(3) Air entrainment. AWA’s based on cellulose tend
to entrain air. In combination with some WRA’s or
HRWRA’s, AWA’s will entrain an excessive amount of air.
When this occurs, an air-detraining admixture must be
incorporated into the concrete mixture to reduce the air
contents to acceptable levels. AWA’s based on gum usually
do not entrain air.
(4) Bleeding. Since AWA’s increase the water
retention of cement paste, virtually no bleeding occurs in
concretes containing these admixtures. However, this would
normally be of little concern in concrete placed underwater.
(5) Retardation. AWA’s based on cellulose tend to
retard the setting time of concrete. Larger dosages of these
AWA’s can retard concrete setting times significantly, in
some cases up to 24 hr. If the delayed setting time poses
problems with other construction operations, an accelerator
can be used to partially offset the retardation. AWA’s
based on gum usually do not retard setting times as much as
those based on cellulose.
(6) Compatibility. AWA’s have little effect on
compressive strengths of concrete. The amount of mixing
water necessary for concrete made with an AWA is greater
than would be necessary for concrete without an AWA. In
many cases the amount of mixing water can be reduced with
a WRA or an HRWRA. In fact, when concretes have w/c
less than 0.50, the use of a WRA will probably be
necessary. When the w/c is less than 0.40, the use of an
HRWRA will be necessary to achieve the flowability
necessary for an underwater placement. Cellulose-based
AWA’s and napthlene sulfonate-based HRWRA’s are
incompatible, and combinations of these should be avoided.
Cellulose-based AWA’s are generally compatible with other
types of HRWRA’s and most WRA’s. Gum-based AWA’s
are generally compatible with most WRA’s and HRWRA’s.
(7) Dosage. The proper dosage of AWA’s, WRA’s,
and HRWRA’s, as well as the compatibility of these
admixtures, must be determined in trial batches prior to the
beginning of any concrete placement. The amount of an
AWA necessary to achieve the desired washout resistance
can vary considerably depending upon the concrete materials
being used and their proportions. An excessive amount of
AWA can render the concrete unworkable, while too little
AWA will not provide adequate washout resistance. Follow
the manufacturers recommendations for dosages and adjust
as necessary in preliminary trial batches. Extreme caution
should be exercised if it becomes necessary to adjust the
dosage of either the AWA, WRA, or HRWRA after the
actual placement begins. A small change in the dosage can
result in a dramatic change in the workability and
cohesiveness of the concrete. When the use of an AWA is
specified, the services of a qualified manufacturer’s
technical representative should be required. The technical
representative should be available during mixture
proportioning studies and be onsite during concrete
placement. The concrete mixture containing the AWA
should be proportioned in the division laboratory if the
mixture is government furnished or in an approved
commercial laboratory if proportioning is a Contractor
responsibility.
(8) Pumping. The cohesiveness imparted by an AWA
actually improves the pumpability of concrete for distances
up to approximately 150 ft. If the pumping distance
exceeds 250 ft, pumping pressures will likely increase
significantly. If the pumping pressures become excessive,
the concrete mixture proportions must be adjusted by adding
water or reducing the amount of the AWA, or the pump
must be relocated to reduce the pumping distance.
Adjusting the mixture proportions in this manner may
reduce the concrete cohesiveness and cause it to be more
susceptible to washout; therefore, relocating the pump, if
possible is the preferable solution.
h. Extended set-control admixtures.
(1) General. These admixtures are relatively new to
the commercial market and were developed to give the
ready-mixed concrete producer maximum flexibility in
controlling the rate of hydration of fresh concrete. They are
typically marketed as a two-component system consisting of
a very strong retarding admixture, sometimes referred to by
the manufacturer as a stabilizer, and an accelerating
admixture, sometimes labeled as an activator by the
manufacturer. These admixtures allow the concrete
producer to take advantage of severely retarded fresh
concrete in several ways, including:
(a) Treating unhardened concrete which is returned to
the plant with the stabilizer so that it can be kept in the
unhardened state, or stabilized, in the truck mixer or holding
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35. EM 1110-2-2000
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hopper for several hours. When the concrete is needed,
cement hydration is normally reactivated by combining
freshly mixed concrete with it before sending it to the job
site. Returned unhardened concrete may also be stabilized
overnight or longer. In these cases, hydration of the cement
in the stabilized concrete is typically reactivated by adding
the activator and then combining the concrete with freshly
mixed concrete before delivering it to the job site.
(b) Treating the freshly mixed concrete at the plant
with the stabilizer so that hydration is retarded to the extent
necessary for very long hauls. Typically, the duration of
retardation is at least 1 or more hours, and use of the
activator may or may not be necessary at the job site,
depending on the dosage of stabilizer used.
(c) Stabilizing plastic concrete in a truck mixer which
has experienced a mechanical breakdown or an unforeseen
delay. In the event of a truck breakdown, the mixer drum
must still be able to turn.
(d) Treating wash water from mixers with the
stabilizing admixture to reduce the need for conventional
wash water disposal methods and thereby mitigating the
environmental concerns. Water consumption is also
reduced. The stabilized wash water is then reused as
mixing water in the concrete batched the next day or after
the weekend.
(2) Stabilizer. The stabilizing admixture slows the rate
of hydrate formation by tying up, or complexing, calcium
ions on the surface of cement particles. It not only forms
a protective barrier around the cement particles but also acts
as a dispersant preventing hydrates from flocculating and
setting. This protective barrier prevents initial set from
occurring.
(3) Activator. The activating admixtures typically
supplied with the extended-set admixture systems are
nonchloride accelerating admixtures conforming to ASTM
C 494, Type C (CRD-C 87).
(4) Effect on hardened properties. Few published data
exist on the effects of extended set admixtures on the
hardened properties of concrete. However, research
indicates the use of a stabilizing admixture may cause finer
and denser hydrates to form, which, in turn, appears to
benefit physical properties of paste.
(5) Dosage. Extended-set control admixtures are
usually delivered in liquid form. Because they are still
relatively new to the concrete industry and because there are
presently no standard specifications for them, their use
should be permitted only after data are supplied by the
concrete supplier that the fresh and hardened properties of
the concrete anticipated for use will not be detrimentally
affected. Manufacturer’s technical representatives should
work closely with the concrete producer to assure correct
dosage rates are established for the particular concretes and
field applications.
i. Antifreeze admixtures. A new group of chemical
admixtures recently introduced into the concrete products
market is known as antifreeze or freezing-protection
admixtures. ASTM standard specifications have not yet
been developed for these admixtures. These materials,
which have been in use in the former USSR since the
1950’s and more recently in Western Europe, are designed
to depress the freezing point of mixing water and thereby
allow concrete to gain strength in an environment below
freezing without suffering the deleterious effects of ice
formation. Concrete made with antifreeze admixtures can
be cured at temperatures below freezing without harming its
performance compared to that of concrete without the
antifreeze admixture and cured at normal temperatures.
(1) Composition. Antifreeze admixtures are similar in
composition to accelerating admixtures, but differences do
exist. ACI 212.3R states that accelerating admixtures
should not be used as antifreeze admixtures. However,
some compounds used as the basis for nonchloride
accelerating admixtures, such as sodium nitrite, calcium
nitrite, and potassium carbonate, have been successfully
used as antifreeze admixtures.
(2) Batching. Antifreeze admixtures are usually
delivered in liquid form and should be added at the mixer
with a portion of the mixing water at a dosage rate
recommended by the manufacturer. They should be added
to the concrete separately and not mixed with other
admixtures, since adverse reactions may occur between
admixtures which can decrease their effectiveness.
(3) Effect on strength. When antifreeze admixtures are
used, early-age compressive strengths are usually
significantly lower than when the admixture is not used and
the concrete is cured at normal temperatures. The strength
gain of concrete which contains an antifreeze admixture and
is cured at temperatures below freezing proceeds at a slower
rate than concrete which does not contain the admixture and
is cured at temperatures above freezing. However, the
strengths of two such concretes may be comparable at later
ages.
(4) Effect on resistance to freezing and thawing. There
is little published documentation describing the frost
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36. EM 1110-2-2000
1 Feb 94
resistance of concrete made with antifreeze admixtures;
however, there is evidence that entrained air bubbles are less
stable when antifreeze admixtures are used. Therefore,
these admixtures should not be used unless acceptable frost
resistance has been verified according to provisions of
ASTM C 494 (CRD-C 87).
(5) Use with reactive aggregates. When sodium nitrite
and potassium carbonate go into solution, if the nitrite or
carbonate ions precipitate out, the sodium or potassium ions
will associate with hydroxide ions to raise the pH of the
pore fluid. Therefore, antifreeze admixtures containing
these materials should not be used with reactive siliceous
aggregates. Concrete made with these materials has also
weakened after repeated exposure to cycles of wetting and
drying. Therefore, antifreeze admixtures containing sodium
nitrite or potassium carbonate should not be used in a
marine environment.
(6) Corrosion of steel. Antifreeze admixtures made
from nonchloride compounds have shown no tendency to
cause corrosion of embedded reinforcing steel. Sodium
nitrite and calcium nitrite reduce corrosion when used in
proper amounts.
(7) Cost benefits. The use of an antifreeze admixture
in concrete can be cost effective. The cost of concreting in
very cold weather may be as much as 50 to 100 percent
higher than that under normal conditions due to increased
equipment and labor costs. The cost of antifreeze
admixtures may be competitive with the higher costs
associated with concreting during subfreezing temperatures.
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37. EM 1110-2-2000
1 Feb 94
Chapter 3
Construction Requirements and Special
Studies
3-1. Construction Requirements
a. General. As the concrete materials design of a
project nears its conclusion, adequate data should be
available related to likely sources of aggregate, water, and
locations of haul roads and access roads to determine if an
onsite or offsite plant is required, and if an onsite plant is
required, the site location. In addition, requirements for
batching plants, mixers, conveying, and placing equipment
must be established and included in the appropriate DM to
guide in the preparation of the plans and specifications.
b. Batch-plant location. The batch plant may be
located onsite or offsite. For a very large dam being built
in a remote location, an onsite plant would be a certainty,
and for a culvert headwall in a metropolitan area, the
concrete would certainly be supplied by a ready-mix firm
acting as a supplier to the Contractor. Between these two
extremes, there are numerous possibilities that will depend
on the scope and location of the work, the nominal
maximum size aggregate required, the desired placing rate,
the anticipated workload of the local ready-mix producers
during the period of construction of the Corps projects, and
the availability or nonavailability of a government-controlled
aggregate source. Specifically, the concrete batching plant
is normally required to be located onsite when the closest
source of ready-mixed concrete is remote from the project,
the nominal maximum size aggregate required makes ready-
mixed concrete impractical and the required placing capacity
cannot be maintained by an offsite plant. An offsite plant
should be considered when the maximum size aggregate is
37.5 mm (1-1/2 in.) or less, commercial concrete plants
exist in the project area, the plants are close enough that the
interval between concrete batching and final placement will
be 1-1/2 hr or less, and the required placement rate can be
maintained. Obviously, on many projects, the decision
between an onsite or offsite plant is not clear cut. The type
of batching and mixing equipment at each commercial plant
should be surveyed and summarized in the concrete
materials DM. If more than one source exists as potential
supplier, all such sources should be investigated and, if
acceptable, be listed in the concrete materials DM. If the
potential exists for either an onsite plant or the use of offsite
commercial source, it should be possible for the bidders to
have the option of setting up and operating an onsite plant
or procuring concrete offsite.
c. Batch-plant type. Available options in batching
equipment include automatic, semiautomatic, partially
automatic, manual, and volumetric batching (ACI 304R,
CRD-C 514, and ASTM 685 (CRD-C 98)). The choice of
the batch-plant control system is dependent on the type of
concrete, the volume of concrete required, the number of
coarse aggregate sizes, and the importance of the structure.
If mass concrete is being placed, an automatic plant will be
specified when four sizes of coarse aggregate are used,
where three sizes of coarse aggregate are used and
75,000 yd3
or more of concrete is involved, or when two
sizes of coarse aggregate are used and more than 100,000
yd3
of concrete is involved. A semiautomatic batch plant
may be specified for mass concrete if not more than three
sizes of coarse aggregate are used and less than 100,000 yd3
of concrete is involved. If cast-in-place structural concrete
is the type of concrete that will be predominant on the
project, the batching equipment specified may be automatic,
semiautomatic, or partially automatic. For major projects
involving important structures or where critical smaller
structures are involved, the optional interlocks and recorders
should be required. If the concrete to be placed on a project
is only for minor structures, any of the above plants are
suitable, plus batch plants having manual controls or
incorporating volumetric batching. The selection of
batching and mixing plant requirements must take into
account both economy and technical requirements for
adequate control of quality. Economic considerations
include initial plant cost, economy of operation (production
rates), and economy in concrete materials, particularly
cement. It may be noted that either an automatic or
semiautomatic plant may be specified where three sizes of
coarse aggregate are used, depending on volume of concrete
involved and the nature of the work. The choice in these
cases is largely dependent on economy. Batch plant types,
including volumetric batching, are discussed in ACI 304R.
d. Mixer type. Stationary tilting-drum mixers should
be used for mixing concrete containing 150-mm (6-in.)
NMSA. For mixing concrete containing 75-mm (3-in.)
NMSA, stationary tilting-drum, pugmill, spiral blade, or
vertical shaft mixers may be used. However, for concrete
containing 75- or 150-mm (3- or 6-in.) NMSA, the
Contractor may choose any stationary mixer if it meets the
required capacity and complies with the uniformity
requirements when tested in accordance with CRD-C 55.
Concrete containing 37.5-mm (1-1/2-in.) and smaller NMSA
may be mixed in stationary mixers or truck mixers. For
minor structures, any of these types of mixers may be used
as well as a continuous mixer with volumetric batcher.
When volumetric batching and continuous mixing are used
for minor structures, the equipment must meet the
requirements of ASTM C 685 (CRD-C 98).
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38. EM 1110-2-2000
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e. Batching and mixing-plant capacity. Careful
consideration must be given to the determination of the
required concrete production capabilities. This
determination is important for both large concrete locks and
dams using an onsite batching and mixing plant and for
smaller structures that may use an offsite plant and trucks
for mixing or hauling or both.
(1) Monolith size. A likely construction progress
schedule should be developed during the PED phase of a
concrete structure. The fixed constraints such as committed
power-on line or lock operation dates and seasonal
constraints should be incorporated into the schedule.
Recently completed similar projects in the area should be
reviewed to determine the maximum placement rates
achieved. The likely placement methods such as crane and
bucket, pump, or conveyor have to be determined and the
structures analyzed so that the largest continuous placements
are identified. The size of the placements are defined by
the placement of construction joints. Construction joints
should be shown on the drawings and should be placed by
the structural designer to coincide with structural features
and reinforcing locations. The thermal study will also
provide input for maximum size of monolith and maximum
lift heights. Construction joints should be located to provide
for as many placements as possible to be approximately the
same volume. If one placement is several times the volume
of all other placements on a project, this will require a much
larger batching and mixing plant capacity than would be
necessary if smaller placements were used. For many
smaller structures, a plant size that will prevent cold joints
will be too small to meet the tentative construction progress
schedule. Regardless of the daily requirements, the plant
capacity has to be such that fresh concrete does not remain
in the form prior to placement of contiguous concrete long
enough to develop a cold joint. The time that concrete may
remain in the form before a cold joint develops is highly
variable. For example, in warm dry climates the time may
have to be reduced 50 percent or more. The time may be
extended by the use of a retarder (ASTM C 494 (CRD-C
87)). As a rule of thumb for initial computation, 2 hr may
be considered the maximum time that cooled concrete is
uncovered before a cold joint will form between the
concrete in place and the new concrete. For uncooled mass
and structural concrete, 1 hr is the maximum time that it
should be uncovered. A cold joint is defined as concrete
that is beginning to set and in which a running vibrator will
not sink under its own weight and a hole is left in the
concrete when the vibrator is slowly withdrawn. When a
cold joint is formed, concrete placement should be stopped
and the cold joint should then be treated as another
construction joint. The selection of the plant size should
provide adequate safety factors to cover the variables.
(2) Traditional placing method. For massive structures
such as locks and dams, the traditional placement method
has been buckets that are moved on trucks and placed with
cranes. There should be a limit of 4 yd3
as the maximum
amount of concrete placed in one pile prior to the
consolidation. A typical lift height of 5 or 7-1/2 ft with an
approximate horizontal layer thickness of about 1-1/2 ft
would require five successive horizontal layers in stepped
progression in 7-1/2-ft lifts and three successive horizontal
layers in stepped progression in 5-ft lifts.
(3) Equation for minimum placing capacity. The
minimum plant capacity may be estimated by using the
following equation or by calculating graphically as
illustrated in paragraph 3-1e(4):
(3-1)
where
Q = Plant capacity, yd3
/hr
W = Width of placement (monolith), ft
B = Bucket size, yd3
b = Width of block per bucket, ft. A block is
assumed to be a square with a height
equal to approximately 1-1/2 ft. For 4-yd3
bucket, b = 8-1/2 ft
h = Maximum time before cold joint forms,
hr. For estimating purposes, use h = 2 for
cooled concrete and h = 1 for uncooled
concrete.
n = Number of layers per lift, normally three
layers for 5-ft lift and five layers for
7-1/2-ft lift.
(4) Graphic calculation of minimum placing capacity.
Figures 3-1 and 3-2 illustrate graphically the placing
sequences for 7-1/2- and 5-ft lifts, respectively, with a 4-yd3
bucket. As shown in Figure 3-1, the required plant output
will reach the maximum after 60 buckets of concrete have
been placed. Each bucket placed after 60 buckets will be
exposed, while 36 additional buckets are being placed.
Therefore, for cooled mass concrete while each placement
may be exposed for 2 hr before cold joint forms, the
required minimum plant capacity will be 36 × 4 = 144 yd3
in a 2-hr period or 72 yd3
per hour. In Figure 3-2, where a
5-ft lift is used, the maximum plant output will be reached
at the sixteenth bucket, and 20 buckets will be placed before
it will be covered. Therefore, for cooled concrete, the
required minimum capacity will be 20 × 4 = 80 yd3
in a
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39. EM 1110-2-2000
1 Feb 94
Figure 3-1. Stepped placement sequence and plant capacity, 7-1/2-ft lift height
3-3

40. EM 1110-2-2000
1 Feb 94
Figure 3-2. Stepped placement sequence and plant capacity, 5-ft lift height
3-4

41. EM 1110-2-2000
1 Feb 94
2-hr period or 40 yd3
per hour. The same results can be
obtained from Equation 3-1.
(5) Other placing methods. If other placing techniques
are likely to be used such as a pump or conveyor, the plant
capacity has to be adequate to supply the unit at a rate near
its rate capacity to avoid plugs or segregation. The capacity
of the plant and placing equipment will have to be adequate
to prevent cold joints in the placements. The capacity
calculated for bucket placement may be used as a beginning
point for plant capacity calculations.
f. Conveying and placing considerations.
Historically, most concrete for Corps structures has been
placed by crane and bucket. Recently, however, the
preferred placing equipment has changed, and conveyors and
pumps are being used to place an increasing amount of mass
and structural concrete, respectively. Mixture proportions,
conveying methods, and placing restrictions must be
considered for each portion of the project during PED to
assure that appropriate concrete is placed in each feature.
For example, it is impossible to pump lean mass concrete
with 75-mm (3-in.) maximum size aggregate, and therefore
buckets, or conveyors must be used. The proportions of the
concrete mixtures must meet the designer’s requirements for
strength, slump, maximum size aggregate, etc., and must be
capable of being placed by the Contractor. The mixture
proportions should not be altered to accommodate a
Contractor’s placing equipment if the designer’s
requirements would be compromised.
g. Use of epoxy resins. All epoxy resin shall be
specified to meet ASTM C 881 (CRD-C 595). The type
and grade for specific uses should be as follows:
Dowels in drilled holes Type IV, Grade 3
Patching and overlays Type III
Bonding new concrete
to old Type V
Crack injection Type IV, Grade 1
Refer to ASTM C 881 for the correct "class" for use at the
anticipated temperature of the surface of the hardened
concrete. During cooler weather, the epoxy resin should be
stored at room temperature for several days prior to use.
3-2. Special Studies
a. General. Often it will be necessary to conduct
tests that extend in scope beyond those listed above. The
need for such tests may develop as a result of the size or
complexity of a project, an unusual characteristic of the
available cementitious materials or aggregates or the
climatic conditions at a project site. The most commonly
required studies are thermal studies followed by abrasion-
erosion studies and mixer grinding studies. Such studies,
when required, should be identified during the feasibility
phase and funding and scheduling should be included in the
project management plan. The results of these studies will
be documented in the appropriate DM.
b. Thermal studies. During the PED for projects
involving concrete structures, it is necessary to assess the
possibility that temperature changes in the concrete will
result in strains exceeding the strain capacity of the
concrete. Although temperature control is generally
associated with large mass-concrete structures, it should be
noted that small, lightly reinforced structures may also crack
when subjected to temperature extremes. Therefore, thermal
studies are required for any important concrete structure.
This may include, but not be limited to, dams, locks,
powerhouses, and large pumping stations.
(1) Material properties needed for a thermal study.
The following concrete material properties should be
determined. Information on cost and time requirements for
the following material properties tests may be obtained from
CEWES-SC.
(a) Heat of hydration. The heat generated will depend
on the amount and type of cementitious materials in the
concrete. The heat of hydration is obtained experimentally
and forms part of the basis for predicting the temperature
rise and decline with time for a concrete (ASTM C 186
(CRD-C 229)).
(b) Adiabatic temperature rise. The temperature rise
in concrete under adiabatic conditions is determined
according to CRD-C 38. The cementitious material types
and aggregates in the concrete so tested should be similar to
those proposed for use in the structure.
(c) Thermal conductivity. Thermal conductivity is a
measure of the ability of the material to conduct heat and
may be defined as the ratio of the rate of heat flow to the
temperature gradient. Numerically, thermal conductivity is
the product of density, specific heat, and diffusivity.
(d) Thermal diffusivity. Thermal diffusivity is a
measure of the facility with which temperature changes take
place within a mass of material (CRD-C 37); it is equal to
thermal conductivity divided by specific heat times density.
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42. EM 1110-2-2000
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(e) Specific heat. Specific heat is the amount of heat
required per unit mass to cause a unit rise of temperature,
over a small range of temperature (CRD-C 124).
(f) Coefficient of thermal expansion. The coefficient
of thermal expansion can be defined as the change in linear
dimension per unit length per degree of temperature change
(CRD-C 39, 125, and 126).
(g) Creep. Creep is time-dependent deformation due
to sustained load (ASTM C 512 (CRD-C 54).
(h) Strain capacity. The ultimate tensile strain
capacity of concrete is determined by measuring the unit
strain at the outer fibers of unreinforced beams tested to
failure under both rapid and slow loading (CRD-C 71).
(2) Time of completion of thermal study. The thermal
and mechanical properties of the concrete are very
dependent on the mineralogical composition of the
aggregates and the cement type used. Therefore, it is
imperative that thermal studies not be undertaken until such
time as the aggregate investigations have proceeded to the
point that the most likely aggregate sources are determined,
and the availability of cementitious material is known. If
changes occur related to the aggregate source or the type of
cementing material as a result of the Contractor exercising
options, supply difficulties, or site conditions, it may be
necessary to rerun a portion of the study to verify the earlier
results. The initial study must be completed before plans
and specifications are finalized.
(3) Temperature control techniques. All the
temperature control methods available for consideration have
the basic objective of reducing temperature rise due to all
factors including heat of hydration, reducing thermal
differentials within the structure, and reducing exposure to
cold air at the concrete surfaces which would create a sharp
thermal differential within the structure. The most common
techniques, in addition to selection of slow heat-gain
cementitious materials, are the control of lift thickness,
placing interval, maximum placing temperature, and surface
insulation. On very large structures, post cooling has been
used (ACI 224R).
(4) Numerical analysis of temperature control
techniques. The analysis of the various temperature control
techniques to determine the combination best suited to a
particular project may be done by computer using a finite-
element analysis program. Interdisciplinary coordination
between materials engineers, structural engineers, and
construction engineers is essential to ensure that the
complex numerical analysis is based on reliable concrete
and foundation properties and realistic construction
techniques. Requests for consultation and assistance in
performing numerical analysis should be made to
CECW-EG. For structures of limited complexity, such as
base slabs, satisfactory results may be obtained by the use
of equations in ACI 207.4R.
c. Abrasion-erosion studies.
(1) General. Damage to the floor slabs of stilling
basins due to abrasion by waterborne rocks and other debris
is a constant maintenance problem on existing Corps
projects. Abrasion-erosion on various projects has ranged
from a few inches to 10 ft, and on occasion, severe damage
has been noted after only a few years of operation.
Hydraulic characteristics have a large effect on erosion and
abrasion and should be considered in the design of
spillways, conduits, and stilling basins.
(2) Test method. An underwater abrasion test method,
ASTM C 1138 (CRD-C 63), is available to allow
comparisons between materials proposed for use in stilling
basins. Results of tests with several types of materials
commonly thought to offer abrasion resistance suggest that
conventional concrete of the lowest practical w/c and with
the hardest available aggregates offer the best protection for
new construction and for repair to existing hydraulic
structures where abrasion-erosion is of concern. The
abrasion tests should be performed to evaluate the behavior
of several aggregate types for use in the stilling basin when
more than one type is available.
(3) Application of test results. Because the costs of
stilling basin repair is often substantial, it may prove
feasible to import aggregate over a long distance for the
concrete in the stilling basin slab if the aggregate in the
project area is soft and the results of the abrasion test shows
the potential for severe erosion. A discussion of stilling
basin erosion should be included in the concrete materials
DM. In some cases where hard aggregate is not
economically available, silica-fume concrete with very high
compressive strength may be used. Apparently, the
hardened cement paste in the high-strength silica-fume
concrete assumes a greater role in resisting abrasion-erosion,
and as such, the aggregate quality becomes correspondingly
less important.
d. Mixer grinding studies. During the investigation
of an aggregate, it may be determined that the material
degrades during handling and mixing. The tendency may be
first noted as a high loss in the Los Angeles abrasion test
(ASTM C 535 (CRD-C 145)). The result of this degrading
is a significantly finer aggregate, and the result will be a
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43. EM 1110-2-2000
1 Feb 94
loss of slump during mixing which will result in an increase
in water demand. Tests should be run by mixing the actual
materials for a time similar to that anticipated on the project
and the mixture proportion adjusted to reflect the finer
grading of the aggregate.
e. Concrete subjected to high-velocity flow of water.
(1) General. Wherever concrete surfaces are to be
subjected to water velocities in excess of 40 ft/s for frequent
or extended periods, special precautions should be taken.
Examples of such surfaces include conduits, sluices, tunnels,
spillway buckets, spillway faces, baffles, and stilling basins.
(2) Quality of concrete. The concrete should have
excellent workability and a low w/c as indicated in Table
4-1. The nominal maximum size of aggregate should be
limited to 37.5 mm (1-1/2 in.) except for the formed por-
tions of the downstream face of spillways for gravity dams
where the maximum size aggregate may be up to 75 mm
(3 in.). In many projects, a special layer of high-quality
concrete, at least 1-ft thick, is specified to be placed over a
lower quality concrete. This is done to keep the overall heat
of hydration lower and for economy. The thickness of high-
quality concrete adjacent to the critical surface should be the
practical minimum that can reasonably be obtained with
conventional placing equipment and procedures, but in no
case less than 1 ft. The high-quality concrete should be
placed integrally with the normal concrete.
(3) Construction joints. Wherever possible, construc-
tion or lift joints should be avoided in the water passages.
Where joints cannot be eliminated, care must be exercised
during the construction to obtain required alignment and
smoothness within the specified tolerance. For example,
grade strips should be used at the tops of lifts to guide the
placement. After the concrete has been placed to grade, the
strip should be promptly removed and the lift surface
adjacent to the form should be smoothed to provide an even
joint when the overlying lift is placed.
(4) Unformed surfaces. Unformed surfaces subjected
to a high-velocity flow of water should be finished with a
steel trowel finish with no abrupt edges, pits, or roughness.
(5) Formed surfaces. Formed surfaces should be
given a Class AHV finish. See paragraph 5-4e for
definitions of classes of finish.
f. Unusual or complex problems. Occasionally during
design or construction, problems may be encountered which
require specialized knowledge not available within the
district or division organization. At this point, consideration
should be given to obtaining the services of CEWES-SC.
The selection of a consultant knowledgeable in concrete
materials will be made with the advice of the Office of the
Chief of Engineers, ATTN: CECW-EG.
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44. EM 1110-2-2000
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Chapter 4
Mixture Proportioning Considerations
4-1. Selection of Concrete Mixture Proportions
The selection of concrete mixture proportions is an
important step in obtaining economical, durable concrete
meeting design requirements. Depending on the types of
structures, the concrete mixture proportions may be selected
by the Government or by the Contractor. When mixture
proportions are to be selected by the Government, the work
will be accomplished by a division laboratory. Proportions
for mass concrete or structural concrete are to be selected in
accordance with ACI 211.1 (CRD-C 99) and other criteria
as described in the following paragraphs of this chapter
whether the work is done by the Government or the
Contractor. Any new materials proposed for use after the
initial mixture proportioning studies must be proportioned
by the division laboratory or the Contractor’s commercial
laboratory using actual project materials in a new mixture
proportioning study.
4-2. Basis for Selection of Proportions
a. General. The process of selecting concrete
mixture proportions is a process of optimization of several
desirable characteristics based on the project requirements.
The characteristics to be optimized are economy, strength,
durability, and placeability.
b. Economy. The primary reason for systematically
determining mixture proportions is economy. The
maximum economy can be achieved by minimizing the
amount of cement used and where appropriate, by replacing
portland cement with usually less expensive pozzolan or
GGBF slag. Economy is also improved by using the largest
nominal maximum size aggregate consistent with the
dimensional requirements of the structures on the project,
and available to the project.
c. Strength. Strength is an important characteristic of
concrete but other characteristics such as durability,
permeability, and wear resistance may be equally or more
important. These may be related to strength in a general
way but are also dependent on other factors. For a given
set of materials, strength is inversely proportional to the w/c.
Since the materials which make up concrete are complex
and variable, an accurate prediction of strength cannot be
based solely on the selected w/c but must be confirmed by
tests of cylinders made from trial batches with the materials
to be used on the project. Strength at the age of 28 days is
frequently used as a parameter for structural design,
concrete proportioning, and evaluation of concrete. When
mass concrete is used, the design strength is generally
required at an age greater than 28 days, generally 90 days,
because mixtures are proportioned with relatively large
quantities of pozzolan or GGBF slag to reduce internal heat
generation. The early strength of mass concrete will be low
compared to that of structural concrete; therefore, mass
concrete should be proportioned for an adequate early
strength as may be necessary for form removal and form
anchorage. A compressive strength of 500 psi at 3 days age
is typical of that necessary to meet form-removal and form-
anchorage requirements.
d. Durability. Concrete must resist deterioration by
the environment to which it is exposed, including freezing
and thawing, wetting and drying, chemical attack, and
abrasion. Concrete must meet three requirements before it
may be considered immune to frost action. It must be made
with nonfrost-susceptible aggregates and a proper air-void
system, and it must achieve an appropriate degree of
maturity before repeated freezing and thawing is allowed to
take place while the concrete is critically saturated. A
proper air-void system is achieved by using an AEA. All
exposed concrete placed by the Corps should be air
entrained unless it is shown to be improper for a specific
situation. The appropriate maturity exists when the concrete
has a compressive strength of approximately 3,500 psi.
Generally, durability is also improved by the use of a low
w/c since this reduces permeability and the penetration of
aggressive liquids.
e. Placeability. Placeability, including satisfactory
finishing characteristics, encompasses traits described by the
terms "workability" and "consistency." Workability is that
property of freshly mixed concrete which determines the
ease and homogeneity with which it can be mixed, placed,
consolidated, and finished. Consistency is the relative
mobility or ability of freshly mixed concrete to flow.
Workability embodies such concepts as moldability,
cohesiveness, and compactability and is affected by the
grading, particle shape, and proportions of aggregate; the
quantities and qualities of cementitious materials used; the
presence or absence of entrained air and chemical
admixtures; and the consistency of the mixture. The slump
test, ASTM C 143 (CRD-C 5), is the only test commonly
available to measure any aspect of the several characteristics
included in the term "placeability." Moldability,
cohesiveness, compactability, and finishability are mostly
evaluated by visual observation, and, therefore, the
evaluations are somewhat subjective. Typically, the
Contractor will evaluate these characteristics from a
different perspective than the government personnel
involved, and within the Contractor’s organization, the
placing foreman may evaluate the placeability differently
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45. EM 1110-2-2000
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than the finishing foreman. In general, the Contractor
would like a high-slump mixture, while the Government
desires a closely controlled slump. The key consideration
must be a carefully proportioned concrete mixture which is
placeable by the conveying and placing equipment to be
used on the project without the addition of water at the
placement site. Simply adjusting the water content of a
mixture that was proportioned for placement by crane and
bucket will not assure that it is pumpable or that such an
adjustment will result in concrete that meets strength and
durability requirements. Mass concrete mixtures are
particularly susceptible to placing problems if not correctly
proportioned. Care must be exercised to assure that the
mortar content of lean, mass concrete mixtures is sufficient
to provide suitable placing and workability. Water-
reducing admixtures should not be used to reduce the paste
content and the resulting mortar content of these mixtures to
a level which causes the mixture to be harsh and
unworkable.
4-3. Criteria for Mixture Proportioning
a. General. The criteria for proportioning should be
determined by the designer based upon the design and
exposure requirements and conditions for the structure
involved. Several sets of mixture proportioning criteria may
be required for each structure to meet different design
requirements. These criteria should be transmitted to the
resident office as outlined in paragraph 6-2, "Engineering
Considerations and Instructions for Construction Field
Personnel."
b. Proportioning criteria.
(1) Maximum permissible w/c. The w/c of both
structural and mass concrete should satisfy the requirements
of Table 4-1.
(2) Structural concrete. For each portion of the
structure, proportions should be selected so that the
maximum permitted w/c is not exceeded and to produce an
initial average compressive strength, fcr , exceeding the
specified compressive strength, f′c , by the amount required.
Where a concrete production facility has test records, a
standard deviation shall be established. Test records from
which a standard deviation is calculated:
• Shall represent materials, quality control procedures,
conditions similar to those expected and changes in
materials, and proportions within the test records shall not
have been more restricted than those for the proposed work.
• Shall represent concrete produced to meet a specified
strength or strengths f′c within 1,000 psi of that specified
for the proposed work.
• Shall consist of at least 30 consecutive tests or two
groups of consecutive tests totaling at least 30 tests.
A strength test should be the average of the strengths of two
cylinders made from the same sample of concrete and tested
at 28 days or at some other test age designated . See ACI
318 for a more detailed discussion.
(a) Required average compressive strength fcr used
as the basis for selection of concrete proportions shall be the
larger of the following equations using the standard
deviation as determined in paragraph 4-3b(2):
fcr = f′c + 1.34s
fcr = f′c + 2.33s - 500
where s = standard deviation
(b) Where a concrete production facility does not have
enough test records meeting the requirements above, a
standard deviation may be established as the product of the
calculated standard deviation and a modification factor from
Table 4-2.
(c) When a concrete production facility does not have
field strength test records for calculation of standard
deviation, the required average strength fcr shall be
determined from Table 4-3.
(d) Evaluation and acceptance of concrete. The
strength of the concrete will be considered satisfactory so
long as the average of all sets of three consecutive test
results equal or exceed the required specified strength f′c
and no individual test result falls below the specified
strength f′c by more than 500 psi. If the above criteria are
not met, the resident engineer will notify the designer
immediately so that the impact of the low strength may be
evaluated. A "test" is the average of two companion
cylinders, or if only one test cylinder is made, then a "test"
is the strength of the one cylinder.
(3) Mass concrete. For mass concrete, the proportions
selected for each quality of concrete for the project shall not
exceed the maximum permitted w/c. Although there is
typically a strength requirement for mass concrete, e.g.
2,000 psi at 1 year, the maximum-permitted w/c for
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46. EM 1110-2-2000
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Table 4-1
Maximum Permissible Water-Cement Ratio (Notes 1 and 2)
Water-Cement Ratios by Mass (for Concrete Containing Cementitious Materials Other
Than 100% Portland Cement, See Note 3)
Severe or Moderate Climate
(Note 4)
Mild Climate, Little Snow/Frost
(Note 4)
Location of Structure
Thin Section
(Note 5) Mass Section
Thin Section
(Note 5) Mass Section
At the water line in hydraulic or waterfront
structures where intermittent saturation is
possible (includes upstream face of dams,
downstream face in overflow sections on dam
where spillage occurs once per year or more
often, and exposed surfaces of lock walls)
0.45 0.50 0.55 0.60
Interior of dams and lock walls and interior of
other large gravity structures where use of two
classes of concrete is practical
-- 0.80 -- 0.80
Ordinary exposed structures, downstream face
of nonoverflow section of dams, downstream
face in overflow section where frequency of
overflow is less than once per year.
0.60 0.60 0.60 0.65
Complete continuous submergence in water
after placement "in the dry" (includes upstream
face of dams below minimum pool elevation)
0.60 0.65 0.60 0.65
Concrete deposited in water 0.45 0.45 0.45 0.45
Pavement slabs on ground:
Wearing slabs
Base slabs
0.50
0.60
--
--
0.55
0.60
--
--
Exposure to sulfate ground water or other
aggressive liquid or salt
0.45 0.45 0.45 0.45
Concrete subjected to high (more than 40 ft/s)
velocity flow of water
0.45 0.45 0.45 0.45
Stilling basins (for flood control and other high-
velocity flow structures)
0.45 0.45 0.45 0.45
Note 1. For all concrete placed in or exposed to seawater, the w/c should be reduced 0.05 below values shown in the table but not lower than
0.45.
Note 2. Mixtures should be proportioned by the division laboratory at the maximum specified slump and air content. They should also be
proportioned at w/c’s 0.02 less than the value shown in the table to allow for batching variability in the field.
Note 3. Where cementitious materials in addition to portland cement are used, the water-cementitious material ratio required is that which would
be expected to give the same level of compressive strength at the time the concrete is exposed to the design environment as would be given
by a mixture using no cementitious material other than portland cement.
Note 4. See Figure 4-1.
Note 5. Largest dimension is 12 in. or less.
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47. EM 1110-2-2000
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48. EM 1110-2-2000
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Table 4-2
Modification Factor for Standard Deviation
No. of Tests1
Modification Factor
for Standard Deviation
Less than 15 See Table 4-3
15 1.16
20 1.08
25 1.03
30 or more 1.00
1
Interpolate for intermediate numbers of tests.
Table 4-3
(See ACI 318, Table 5.3.2.2)
f ′c fcr
Less than 3,000 psi f ′c + 1,000
3,000 - 5,000 psi f ′c + 1,200
More than 5,000 psi f ′c + 1,400
acceptable durability will often have a corresponding
strength in excess of this value when the mixture meets the
criteria in Table 4-1. Concrete that will be subjected to
repeated freezing-and-thawing cycles while critically
saturated with water must have developed a strength of
about 3,500 psi before being allowed to freeze and thaw. If
the maximum values in Table 4-1 are not low enough to
ensure this strength under the anticipated environmental
conditions and required duration of curing and protection,
then the w/c (or water-cementitious material ratio) must be
lowered or the required duration of curing and protection
increased. To ensure that no more than 2 in 10 tests fall
below the strength corresponding to the required w/c, the
required average strength is determined as follows:
fcr = f′c + ts
where
t = 0.854 for 30 tests or less; 0.842 if more than 30
tests are available
s = standard deviation
Where results of fewer than 30 tests are available, the
average strength should exceed f′c by 600 psi. Mixtures
will be proportioned to meet the required average strength
except where the required w/c provides strength in excess of
the design strength. The basis for the equation and the
computation of standard deviation is found in ACI 214.
(4) Nominal maximum aggregate size. The nominal
size of aggregate recommended for various types of
construction is listed in Table 2-2.
(5) Water content. The water requirement is a
function of the nominal maximum size aggregate, the
aggregate grading, the required air content, and the required
slump. Given these parameters, the approximate starting
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49. EM 1110-2-2000
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water content for mixture proportioning studies can be
determined from Table 6.3.3 of ACI 211.1. In the range of
normal concretes, a given combination of aggregates
requires an approximately constant amount of water per
cubic yard of concrete for a given slump regardless of the
w/c. In mass concrete, the water requirement is maintained
low by the use of a large nominal maximum aggregate size
and by the close control of grading.
(6) Cement content. The quantity of cementitious
materials will be determined based on the maximum w/c
and the estimated water requirement selected for the portion
of the structure involved. In mass concrete, the usual low
water requirement results in a low cement requirement
which is one of the means of reducing the amount of heat
developed by hydration.
(7) Proportioning with pozzolans or GGBF slag.
Major economic and temperature rise benefits are derived
from the use of pozzolans, blended cement, or GGBF slag.
Therefore, concrete should be proportioned with the
maximum amount of these materials that will satisfy the
structural, durability, and other technical requirements as
appropriate and be economically beneficial. Use of
pozzolans and GGBF slag in mass concrete provides a
partial replacement of cement with a material which
generally generates less heat at early ages. The effects of
these materials on the properties of freshly mixed concrete
vary with the type and fineness; the chemical, mineralogical,
and physical characteristics of the material; the fineness and
composition of the cement; the ratio of cement to pozzolan
or GGBF slag; and the total mass of cementitious material
used per unit volume of concrete. Often, it is found that the
amount of mixing water required for a given concrete slump
and workability is lower for mixtures containing pozzolans
or GGBF slag than for those containing only portland
cement. Air-entraining admixture needs may be reduced by
up to approximately 20 percent or increased by over 60
percent depending on the characteristics of the pozzolan or
slag. Therefore, it is important to evaluate the pozzolan or
slag using representative material samples during the
laboratory mixture proportioning study. The dosage rate of
chemical admixtures should generally be based on the total
amount of cementitious material in the mixture. The
proportion of cement to pozzolan or GGBF slag depends on
the strength desired at a given age, heat considerations, the
physical and chemical characteristics of both cement and
cement replacement material, and the cost of respective
materials. As a safety precaution against the possibility of
increased alkali-silica reaction in concrete containing small
(pessimum) amounts of certain pozzolans, the quantities of
fly ash and natural pozzolan used in concrete should not be
less than 15 percent by mass of total cementitious material.
ASTM Type I (PM) should not be specified because of the
possibility that it would contain the pessimum amount of
pozzolan. The selected replacement quantities should be
discussed in the concrete materials DM. This guidance will
then be used by the division laboratory to proportion project
concrete mixtures using materials submitted by the
Contractor. Due to differences in their densities, a given
mass of pozzolan or slag will not occupy the same volume
as an equal mass of portland cement. The determination of
w/c, by absolute volume equivalency, when pozzolan or slag
is used is described in ACI 211.1.
4-4. Government Mixture Proportions
a. General. When concrete is being placed in a
structure requiring the use of the guide specification for
mass concrete, CW-03305, the mixture proportions are
determined at a division laboratory using materials provided
by the Contractor which are representative of those to be
used in the project. Those division laboratories authorized
to test concrete materials are listed in ER 1110-1-8100,
"Laboratory Investigations and Materials Testing."
Proportions for mass concrete or structural concrete are to
be selected in accordance with ACI 211.1 and other criteria
as described in the following paragraphs of this chapter.
b. Coordination between project, district design
personnel, and the division laboratory. The criteria for
proportioning the concrete mixtures to meet the requirement
of each type of concrete required in a project is provided to
the project personnel in detail in paragraph 6-2,
"Engineering Considerations and Instructions for Field
Personnel." The project personnel should notify the division
laboratory of the required proportioning criteria at the time
that the samples are transmitted from the Contractor to the
laboratory. Much time is lost when several tons of
aggregate and cement are delivered with no previous
notification by Corps project personnel that the material was
coming and no indication of proportioning criteria required.
Since the specification indicates when the Contractor should
expect starting mixtures after he submits his materials
samples, close coordination between the Corps personnel on
the project and in the division laboratory is essential, not
only to assure that mixture proportions meet the project
needs but also to avoid delay claims by the Contractor. The
"Guide Specification for Mass Concrete," CW-03305,
requires the designer or specification writer to state the
number of days prior to the start of concrete placing that
materials for mixture proportioning studies must be
submitted to the division laboratory. Timely submittal of
these materials is the responsibility of the project office.
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50. EM 1110-2-2000
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c. Sampling of materials. Guide Specification
CW-03305 outlines the procedure by which samples are to
be taken by the Contractor for mixture-proportioning studies.
The Contractor is required to test the aggregates for quality
and grading before shipment to the laboratory. These
samples are to be taken under the supervision of the
Contracting Officer. It is important that this requirement is
followed. The most common problems arising from lack of
attention to these details are samples arriving at the division
laboratory which do not meet project grading requirements
or are not representative of the materials that are actually to
be used or both. Both problems may lead to delays of
concrete placements or the necessity for considerable field
modification of the mixture proportions. The division
laboratory should test submitted materials to determine that
they meet specification requirements prior to using them to
develop mixture proportions. The need for the samples that
are submitted to be representative extends to all the
materials in the concrete, including cement, pozzolans,
GGBF slag, and chemical admixtures.
d. Data supplied by division laboratory to project.
For each type of concrete required on the project, the
division laboratory should select initial proportions that
satisfy the mixture criteria provided by the project
personnel. The batch amounts of each constituent in a cubic
yard should be reported in the saturated-surface dry (SSD)
condition. The amounts of chemical admixtures such as air-
entraining and water-reducing admixtures will be reported
as fluid ounces per 100 lb of cementitious materials.
Strength data will be provided for each type of concrete to
the extent that it is available by the time the proportions are
transmitted to the project. As a minimum, 24-hour, 7-day,
28-day, and design-age strengths should be available prior
to the start of placement. A regression analysis of
accelerated strength at a later age should be computed to
determine the correlation coefficient and 95 percent
confidence limits (see ACI 214.1R). The mixture
proportions provided for each type of concrete should
include a family of curves of strength versus water-
cementitious materials ratio at various ages.
e. Adjustment of government mixture proportions.
The mixture proportions provided by the division laboratory
provide starting mixtures meeting the project criteria.
However, when these proportions are used in the first
batches of concrete produced by the Contractor’s plant, it is
not uncommon for the concrete to be deficient in one or
more of the control parameters of the specifications. The
most common deficiency is in the slump. The laboratory
will report mixture proportions based on the aggregates in
an SSD condition. A common cause of an increase in
slump is the failure to properly adjust for free moisture in
the aggregate, particularly the fine aggregate. Low slump
is normally not a problem if concrete is batched and mixed
on site unless rapid slump loss occurs. Variations in the
chemical or physical properties of cement or pozzolan are
the most common causes of rapid slump loss although
transporting and placing operations may also contribute to
the problem. Assuming all materials and transporting and
placing equipment and operations meet specification
requirements, the most practical solution for dealing with
rapid slump loss is to increase the slump at the mixer to the
degree necessary to have a slump at the forms which is
within the specification limits. The w/c should be
maintained constant if the slump is increased. Care should
be taken to determine if the addition of cementitious
materials necessary to maintain a constant w/c will
detrimentally affect the thermal properties of the concrete or
nullify results of a thermal stress analysis. Adjustments of
the dosage of air-entraining admixture by the Contractor are
required as needed to maintain air contents within the
specified range. As gradings of individual coarse aggregate
size groups change, the proportions of the size groups
should be adjusted so that the combined coarse aggregate
grading approximates the maximum density grading. The
maximum density grading may be computed using Equation
A5.3 in ACI 211.1. As the combined coarse aggregate
grading approaches the maximum density grading, the void
content of the mixture is reduced and more mortar is
available for placeability, workability, and finishability.
Solution of the percentage of each size group can usually be
done such that the combined coarse aggregate grading is
generally within 2 or 3 percent of the maximum density
grading. Trial and error may be used in selecting the
percentage of each size group necessary to produce a
combined coarse aggregate grading which approximates the
maximum density grading; however, proprietary computer
programs are also available. Contact CECW-EG for the
available computer programs. Adjustments in the
percentage of fine aggregate is less common, but slight
changes may be necessary to compensate for significant
changes in grading over an extended period of production.
Adjustments to government mixture proportions are to be
made by government personnel. Changes in aggregate and
water batch weights to compensate for free moisture in
aggregates are made by the Contractor and are not
considered adjustments to mixture proportions. Division
laboratory personnel should be present and prepared to make
adjustments in mixture proportions when the Contractor
initiates concrete production on a project and after periods
of batch plant shutdown such as winter shutdowns or
prolonged strikes. Procedures for making adjustments are
given in ACI 211.1 and will be made on an absolute volume
basis. The mortar volume should remain constant and
changes in any one mortar constituent such as water, fine
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51. EM 1110-2-2000
1 Feb 94
aggregate, air, or cementitious material content should be
compensated for by changes in another mortar constituent
without changing the w/c. It is important that adjustments
to the government mixture proportions be made during plant
shake-down, before any concrete is placed in the structure.
4-5. Evaluation of Contractor-Developed Mixture
Proportions
a. General. The Contractor should submit his
mixture proportions for review prior to initiating concrete
placement. The mixture proportions should be developed in
accordance with ACI 211.1.
b. Reviewing contractor submittals.
(1) Minor structures. When the concrete being placed
is in a minor structure, the concrete will almost always be
supplied by a ready-mixed concrete producer. The mixture
proportions will normally be submitted as a tear sheet from
the producer’s catalog or as a data sheet from a local
commercial laboratory which was retained at some time to
prepare a series of mixtures for the producer to market.
Review of these submittals should include a determination
that the type of cement used, the air-entraining admixture,
and the aggregate source are the same as will be used on the
project and that each constituent meets the specification
requirements. Test cylinder data submitted by the
Contractor should not be more than 180 days old. The w/c,
f′c, and fcr must satisfy the contract requirements.
(2) Cast-in-place structural concrete. Because the
structures for which this guide specification is applicable are
important structures involving water control and power
production, the specification requirements provided to the
Contractor for proportioning the concrete mixtures are
similar to those followed by the division laboratory when
the Government is required to proportion the mixture. The
review of the submitted mixture proportions should assure
the following:
(a) Cementitious materials. The submitted mixture
must be proportioned using the same cementitious materials
as will be used in the project. This should include type,
manufacturer, mill of origin, and time of manufacture. If a
pozzolan is to be used, the Contractor’s submittal should
state whether the percentage of replacement is based on
mass or volume.
(b) Aggregate. The aggregate used in proportioning
the mixture should represent the current production of
whichever source the Contractor selects. Quality tests and
grading test results should be submitted showing that the
aggregates meet specification requirements. Batch amounts
for aggregates should be listed in the SSD condition unless
some other basis is agreed on.
(c) Admixtures. The admixtures used in proportioning
the mixture should be from the same stock that the
Contractor has purchased for use on the project or from the
current stock of the ready-mix producer for the project. All
admixtures should meet the project specifications and the
dosages should be listed.
(d) Test results. The w/c and required strength test
results should be reviewed to assure that they match project
requirements. Air contents and slumps should be at the
upper limits of the specification requirements.
(e) Placeability. The mixtures must be proportioned
to provide the necessary placeability for the conveying and
placing equipment that the Contractor proposes to use. For
instance, concrete that will be pumped may be proportioned
differently than concrete that will be delivered by crane and
bucket, or directly from the truck mixer, or by tremie pipe,
etc.
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52. EM 1110-2-2000
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Chapter 5
Preparation of Plans and Specifications
5-1. Selection of Guide Specification for Concrete
a. General. The use of guide specifications is
prescribed by ER 1110-2-1200, "Plans and Specifications."
Guide specifications for concrete are used to ensure that the
requirements for concrete construction for all projects will
be consistent and that the concrete produced will be uniform
in properties, of required quality, and economical. There
are several guide specifications available for concrete placed
on Corps of Engineers civil works projects. These guide
specifications should be used in every case, with the only
exceptions being for situations requiring the use of special
concrete applications not covered in guide specifications.
Changes should be limited to minor technical changes unless
approved in the DM. No changes should be made in the
format. The completion of project specifications will be
based on the approved concrete materials DM.
b. Guidelines for selection. If the project for which
specifications are being prepared involves mostly mass
concrete as in a lock or dam, Guide Specification
CW-03305, "Mass Concrete," should be used. For an
important structure, other than a lock or dam, such as a
powerhouse superstructure, bridge, fish hatchery complex,
visitor center, tunnel lining, major pumping station, intake
structure, or other structures appurtenant to embankment
dams where reinforced concrete is required, the Guide
Specification CW-03301, "Cast-in-Place Structural
Concrete," should be used. If the project is a recreational
site, road relocation, or other project involving small
amounts of concrete in structures such as culvert headwalls,
comfort stations, residences, or low headgate structures, the
Guide Specification CW-03307, "Concrete (for Minor
Structures)," should be used. There may be instances where
more than one guide specification will be necessary on the
same project. When this is the case, it will be important to
precisely outline in the specification and on the plans which
specification applies. The Guide Specification CW-03362,
"Preplaced Aggregate Concrete," is chiefly applicable for
repairs to damaged or deteriorated concrete structures.
c. Use of state specifications. The specifications of a
state agency, such as a highway department, may be
substituted for all or parts of the Guide Specification
CW-03307, "Concrete (for Minor Structures)," when the
work being accomplished will ultimately be operated or
maintained or both by the state in which it is located or
when savings will result due to the familiarity of local
contractors with the more usual specifications. One area
where savings may result would be in the substitution of
state requirements for aggregate quality and grading when
it is known that this is the material produced in greatest
quantity by local aggregate producers.
d. Use of abbreviated specifications. For very small
concrete placements, it may be justifiable to use an
abbreviated specification of one or two pages in length
produced by editing a state specification or the Guide
Specification CW-03307, "Concrete (for Minor Structures)."
Such abbreviated specifications should be considered when
the only concrete on the project is being placed in picnic
table bases, light bases, small culvert headwalls, or other
small noncritical structures.
5-2. Guide Specification "Concrete (for Minor
Structures)," CW-03307
a. General. This guide specification provides
requirements for concrete of adequate quality for minor
structures. All concrete must be air-entrained.
b. Cementitious materials options. The intent of the
Guide Specification CW-03307, "Concrete for Minor
Structures," is to allow the Contractor maximum flexibility
to use locally available cementitious materials. Accordingly,
the optional use of blended hydraulic cement would be
allowed if such material is reliably available in the project
area. Low-alkali portland cement would be a specified
option if locally available aggregates are known or
suspected to be potentially deleteriously alkali reactive.
Increased resistance to sulfate attack may be obtained with
blended hydraulic cement by specifying a suffix of MS
following the type of designation. All specifications must
allow the use of pozzolan; reference paragraph 2-2 of this
manual.
c. Selection of compressive strength. The required
specified compressive strength will be determined by the
structural designer. Normally, a specified compressive
strength (f′c) of 3,000 psi at 28 days is a reasonable and
attainable value in rural areas and remote locations where
many of the minor structures are located. Higher values
may be specified if required. The value specified should be
confirmed as adequate by the designer in every case. If
durability is a limiting design factor, the maximum w/c shall
normally be limited to 0.50. Lower values may be specified
if required. See Table 4-1.
d. Selection of nominal maximum aggregate size. The
largest nominal maximum size aggregate incorporated into
the minor structures intended to be covered by this
specification is 37.5 mm (1-1/2 in.). If thin sections are
involved or there is interference from reinforcement,
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53. EM 1110-2-2000
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19.0-mm (3/4-in.) nominal maximum size aggregate will be
specified. Generally, for sections 7-1/2 in. or less in width,
heavily reinforced floor and roof slabs, and all sections
where space is limited and surface appearance is important,
19.0-mm (3/4-in.) maximum size aggregate will be
specified. For sections over 7-1/2 in. wide and in which the
clear distance between reinforcement bars is at least
2-1/4 in., the maximum size aggregate specified shall be
37.5 mm (1-1/2 in.).
e. Finish requirements. This guide specification
requires a floated finish on unformed surfaces with an
optional paragraph for a steel-trowel finish. A float surface
will be adequate for most of the concrete covered by this
specification; however, for shop or office floors, other areas
where frequent cleaning is necessary, and areas to be
painted or covered by other floor coverings, a steel-trowel
finish should be specified.
5-3. Guide Specification "Cast-in-Place Structural
Concrete," CW-03301
a. General. The Guide Specification CW-03301, "Cast-
in-Place Structural Concrete," is for use on important
reinforced structures; therefore, it is not intended to be
edited except to select available options. Guidance for the
selection of the options is provided in the following
paragraphs. Any substantial departures from the guide
specifications must be included in the appropriate DM for
approval.
b. Testing of cementitious materials. Essentially, there
are two options provided in the guide specification to define
the required preconstruction testing or certification of
cement and pozzolan. The procedures to be followed when
cements and pozzolan are to be sampled and tested by the
Government prior to their use in the construction to
determine compliance or noncompliance with the
specifications are specified. The Contractor may also elect
to use cement or pozzolan from a source which has been
prequalified by the Government. These guide specifications
define those conditions that must be met for the acceptance
of cementitious materials on the basis of a manufacturer’s
certification of compliance accompanied by mill test reports.
The decision to use the more restrictive paragraphs should
be based on the criticality of the structure involved.
Generally, government testing will be used for powerhouse
structures and any structures appurtenant to locks and dams
that control water, to include tunnel lining, large gate
structures, intake structures, stilling basins, and major
bridges. Certification accompanied by mill test reports, will
suffice for fish hatchery structures, maintenance structures,
and others not specifically designed for the control of water
downstream. If cementitious materials are to be tested by
the Government, the U.S. Army Engineer Waterways
Experiment Station (ATTN: CEWES-SC) should be
contacted for a current cost. Cement or pozzolan sources
that are prequalified must also be periodically tested during
construction at CEWES-SC, and the tests must be funded.
c. Admixtures and curing compounds. Optional
paragraphs of CW-03301 provide for air-entraining
admixtures, water-reducing admixtures, and curing
compounds to be accepted on the basis of either
preconstruction testing by the Government or certifications
of compliance submitted by the Contractor. The decision as
to which option to use for the admixtures or curing
compounds should be based on the criticality of the
structures involved and on past experience with the products
and suppliers in the project area. If problems have occurred
on other projects, then the product should be tested by the
Government to assure compliance.
d. Testing of aggregate. The division laboratory which
will receive the samples should be contacted and the sample
sizes and the number of days required to evaluate the
aggregates established. The number of days listed for the
testing of the aggregate should be chosen to be long enough
to provide for unforeseen delays at the laboratory so that the
Contractor claims which would result if the evaluation were
delayed can be avoided.
e. Nonshrink grout. The type(s) of nonshrink grout to
be used are to be selected by the Contractor in accordance
with ASTM C 1107 (CRD-C 21). The decision as to the
type of nonshrink grout should be based on the application,
exposure conditions, and the manufacturer’s
recommendations. If severe exposure conditions are
anticipated, testing should be performed on the types of
nonshrink grouts specified to assure their adequacy. If the
Contractor selects a Grade A prehardening volume adjusting
grout, the space to be grouted must be confined on all sides.
f. Cementing materials option. The inclusion or
exclusion of available cementing materials options in the
preparation of project specifications must be based on and
supported by the results of the investigations outlined in
Chapter 2 of this document. The guide specifications
provide, as options, those types of portland cement and
blended hydraulic cements generally used for cast-in place
structural concrete, and the Contractor should be allowed the
widest choice possible subject to specific suitability and
availability. The Contractor must be allowed the option of
using fly ash.
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54. EM 1110-2-2000
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g. Specifying aggregate. The coarse aggregate gradings
and aggregate quality to be specified in the guide
specifications must be based on and supported by the
investigations outlined in Chapter 2 of this document. The
ASTM C-33 (CRD-C 133) sizes selected as options will
depend on the nominal maximum size aggregate available
and appropriate for use in the various project structures as
specified in the guide specifications. The selection of the
nominal maximum size coarse aggregate will also be based
on the aggregate investigation. If technically feasible, the
size number selected will correspond to those available in
whatever commercial aggregate sources are listed. Note that
size No. 1, 2, 3, and 357 will not be specified since the
nominal maximum size represented by these designations
exceeds 37.5 mm (1-1/2 in.), and size No. 7 and 8 are for
"pea gravel" sizes not normally used in structural concrete.
h. Strength. The paragraph in part one of CW-03301
entitled "Design Requirements" lists the strengths required
for the various portions of the structure. It is necessary for
the designer to determine what strength is required and the
age at which the strength is needed or the design age.
Typically, this is 28 days; however, if construction or
operational loads are not anticipated for some longer period
of time, economies can be realized in the concrete by
proportioning concrete mixtures to attain design strengths at
later ages such as 90 or 180 days. It should be noted,
however, that durability requirements might result in higher
strengths due to the w/c requirements.
i. Batch-plant capacity. The computation of batch-plant
capacity for cast-in-place structural concrete will be based
on an assessment of the likely placement sequence on the
project. See Chapter 3 of this manual for guidance in
selecting the batch-plant capacity.
j. Batch-plant controls. The batch-plant control system
specified for cast-in-place structural concrete may be
partially automatic, semiautomatic, or automatic. The
semiautomatic plant should be provided with interlocks and
recorders if the project includes major structures. If
technically feasible, the batch-plant requirements should
coincide with the equipment which is locally available. See
Chapter 3 of this manual for more guidance on selection of
batch-plant type.
k. Concrete deposited in water. The optional
paragraph, CW-03301, entitled "Placing Concrete Under-
water" will be included in all specifications for projects
which include underwater placement of concrete. The
decision to use underwater placement in lieu of dewatering
must be discussed in the Concrete Materials DM.
l. Finishing unformed surfaces. Subparagraphs are
provided in paragraph 8-3 entitled "Finishing" to provide an
abrasive aggregate finish, a broom finish, or a bonded two-
course floor. The abrasive aggregate finish or broom finish
should be applied in those areas where slippery floor
surfaces would present a problem. A bonded two-course
floor would be an option for a warehouse area or other
surface exposed to heavy loads, traffic, and abrasion.
m. Sheet curing. Sheet curing may be specified for
horizontally finished surfaces such as roof slabs, floors not
subject to public view, or floors that are to be covered with
tile or resilient flooring by listing the areas to be so cured.
Polyethylene film shall not be used unless it is coated with
burlap or other materials.
n. Areas to be painted. If the project includes large
areas of concrete surfaces to be painted, they should be
impervious sheet cured, moist cured, or cured with a
chlorinated rubber base curing compound specified by
reference to ASTM C 309, (CRD-C 304) Class B.
o. Finishing formed surfaces. Optional subparagraphs
are included in the paragraph entitled "Formed Surfaces" to
provide for various finishes to achieve desired architectural
effects. The selection of the optional paragraphs will
depend on architectural requirements. The architectural
drawings should be consulted when preparing this
paragraph. When extensive use of architectural finishes are
planned, guidance for expanded specifications may be
obtained from CECW-EG. ACI 303R is an excellent
reference.
p. Floor tolerance. The optional paragraph in part 3,
CW-03301, entitled "Slab Tolerance by F-number System"
may be used as this technology becomes available in the
local project area or immediately as a very flat floor is
necessary. Reference the discussion in Chapter 8 of this
manual before specifying the F-number system.
5-4. Guide Specification "Mass Concrete,"
CW-03305
a. General. This specification is intended for large
civil works structures of predominately mass concrete.
These structures are almost always important water control
structures. This guide specification is the most restrictive of
the guides for concrete construction and is intended to be
used unedited except for selecting available options, unless
a deviation has been approved in advance in the materials
DM. Guidance for the selections of some of the options is
provided in the following paragraphs.
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55. EM 1110-2-2000
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b. Sampling of aggregates. To complete the paragraph
in part 2, CW-03305, entitled "Aggregates," CRD-C 100 and
the concrete materials DM should be consulted. The
division laboratory that will receive the samples should be
contacted, and the sample sizes and the number of days
required to evaluate the aggregate confirmed and
established. The number of days listed for the testing of the
aggregate should be chosen to be long enough to provide for
unforeseen delays at the laboratory so that the contractor
claims which could result if evaluation were delayed can be
avoided. It may be necessary to have some overlap in the
time required for aggregate quality testing and the time
required for mixture proportioning studies so as to not delay
the start of construction. Close coordination between the
project office and the division laboratory is important.
c. Mixture proportioning studies. Mixture
proportioning studies will be completed at the assigned
Corps of Engineers division laboratory. It is necessary to
insert the address of the assigned division laboratory in
Guide Specification CW-03305. The quantities required for
the mixture proportioning studies will be furnished by the
laboratory. Materials shipped to the laboratory should be
accompanied by the required contractor’s quality and
grading test reports. Government quality tests should be
performed in the division laboratory as judged necessary,
prior to mixture proportioning studies.
d. Testing cementitious materials. Current costs for
testing hydraulic cement, pozzolan, and GGBF slag should
be obtained from the Waterways Experiment Station
(ATTN: CEWES-SC). The cost for testing of cementitious
materials will be included in Guide Specification
CW-03305. Samples and funding of testing is required even
though prequalified sources are selected.
e. Surface requirements. Several classes of finish are
available in CW-03305 to be employed as described in the
following paragraphs.
(1) Class A finish. Class A finish is specified for
surfaces of structures where excellent appearance at close
range is important. Examples of Class A finish include
exterior walls of buildings of all types such as
superstructures of powerhouses and pumping plants, interior
surfaces of such walls when no other finish treatment is to
be added, floodwalls, and parapets, and other ornamental
structures on dams. The required form materials for
Class A finish are limited to new, well-matched tongue-and-
groove lumber or new plywood panels as specified in the
paragraph entitled "Materials" in Part 2 of CW-03101. The
forms should be clean, tightly set, and securely anchored to
prevent grout leaks.
(2) Class AHV finish. Class AHV is for finishes
exposed to a high-velocity (greater than 40 fps) flow of
water. Examples of this type of surface include lock filling
and emptying ports, lock culverts, outlet works, and spillway
tunnels. The forms should be strong and held rigidly and
accurately to the specified alignment. The materials for
forms are the same as Class A finish except that steel forms
may be used.
(3) Class B finish. This finish is specified for
permanently exposed surfaces where excellence of
appearance treatment is not as paramount. Examples
include concrete dams and appurtenances (except where
Class A finish is required), retaining walls, floodwalls,
exposed surfacing of culverts, and outlet works.
(4) Class C finish. This finish is specified for areas that
are not normally exposed to public view but will not be
permanently covered with backfill. Examples include
machinery rooms and interior passageways in large projects.
(5) Class D finish. This finish is specified for concrete
surfaces where roughness and irregularities are not
objectionable. Examples include bulkhead faces of
monoliths in mass concrete structures and surfaces against
which backfill will be placed. The chief requirement of the
form is that it be watertight.
(6) Absorptive form lining. Absorptive form lining
should not be specified. Numerous problems have resulted
due to the use of absorptive form linings: small air bubbles
remaining immediately below a thin surface skin of mortar,
form lining sticking to concrete surfaces, and in general, the
results have not justified the extra cost.
f. Appearance. The paragraph in part 3 entitled
"Curing and Protection" of CW-03305, "Guide Specification
for Mass Concrete," provides for those surfaces on which
discoloration would be aesthetically undesirable and
therefore need to be removed. The surfaces are those
permanently exposed to view by the general public. In
areas where the only available curing water is likely to stain
or where aggregate impurities contribute to staining, it may
be economically infeasible to prevent or remove all staining,
and staining should be removed only on those surfaces
constantly exposed to public view on which staining would
be aesthetically troublesome.
g. Cementitious materials option. The inclusion or
exclusion of available cementing materials options in the
preparation of project specifications must be based on and
supported by the results of the investigation outlined in
Chapter 2 of this manual. The guide specification provides
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56. EM 1110-2-2000
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for those types of portland cement and blended hydraulic
cements generally used for mass concrete and available in
the project area. Consult the materials DM for those
cementitious material options which should be allowed. The
use of fly ash will be permitted.
h. Bid schedule for cementitious materials options.
Provisions should be made in the bid form for optional
bidding on all the available and acceptable cementitious
materials. The estimated quantities of portland cement,
blended hydraulic cement, and GGBF slag should be
expressed in units of mass. The quantities may vary
between the various cements due to differences in required
mixture proportions and density. The estimated quantities
of pozzolans should be expressed in units of solid volume
(cubic feet). This allows for variations in density dependent
on the source selected by the Contractor. The estimated
quantities of both cement and pozzolan should be derived
from information gained in the preparation of preliminary
mixture proportions during the preparation of the concrete
materials DM.
i. Retarder. The Contractor may use a retarder at his
option except in areas where retardation is considered to be
detrimental. A retarder is appropriate when uncooled
concrete is to be placed in very hot weather and the placing
schedule is such that a danger of cold joints exists or
problems in finishing may be anticipated. Retarders are also
applicable to special structures in which revibration will be
used to ensure low permeability.
j. Water reducers. The mandatory use of WRA’s
should be restricted to locations where there is an economic
advantage to the Government. A Contractor’s request to use
a WRA in structural concrete should be approved unless its
use is harmful in a given situation. The material should
meet the requirements of ASTM C 494, (CRD-C 87) Type
A or D, unless retardation would be detrimental to the work,
in which case only Type A should be specified. Since the
economic benefits resulting from the use of an admixture
usually cannot be evaluated until the Contractor has made
his choice of materials, the bidding schedule should include
a split bid for a WRA. The first item includes for
mobilization and demobilization costs of storing, dispensing,
and recording the admixture. When the laboratory
evaluation indicates no economic benefit from use of the
admixture, it is not necessary to approve its use.
k. Fine aggregate grading requirements. Fine
aggregate grading is a major factor affecting the unit water
requirement, fine aggregate-coarse aggregate ratio, and
cement content of a concrete mixture. That portion of the
fine aggregate finer than the 150-µm (No. 100) sieve has the
most pronounced effect on these factors. While it is
possible to proportion a workable normal strength concrete
mixture using most naturally occurring sand deposits, those
gradings that fall within the limits listed in the guide
specifications are more practical, generally requiring less
cement and water for adequate workability. Beneficiation
of the natural deposits can be accomplished by use of
equipment which will reject a specific size portion or which
will blend in a finer sand will usually be cost effective.
Most natural river sands are deficient in the sizes finer than
the 150-µm (No. 100) sieve. This fine sand is often
available and used in local asphaltic concrete paving mixes.
The finess modulus (FM) is most useful in controlling the
consistency of the fine aggregate during construction. The
proposed fine aggregate grading requirement should be
presented in the concrete materials DM. When
manufactured sand is allowed in the project specifications,
the optional requirement limiting the amount of material
passing the 75-µm (No. 200) sieve should be used if the
Contractor chooses to use manufactured sand. See
paragraph 2-3b(8) of this manual entitled "Fine Aggregate
Grading Requirements."
l. Coarse aggregate grading requirements. Whenever
the maximum aggregate size is less than 150 mm (6 in.), the
inapplicable portion of the table on coarse aggregate
gradings should be deleted in the project specifications.
When coarse aggregate is to be supplied from commercial
sources in an area where local practice provides size group
separations other than those in the table, the table may be
appropriately modified providing the local grading practice
permits adequate control of grading. The revised grading
should be presented for approval in the concrete materials
DM. Rescreening and washing will be required for all
mass-concrete structures.
m. Batching and mixing plant.
(1) Type of plant. The specifications provide for two
alternates, an automatic batching plant or a semiautomatic
batching plant. The selection of batch-plant type will be
based on and supported by the concrete materials DM. The
paragraph entitled "Equipment" provides the option of an
onsite or offsite plant. The selected option will also be
based on the concrete materials design memorandum.
(Reference Chapter 3 herein.)
(2) Capacity. The paragraph in part 2 entitled
"Capacity" of CW-03305, "Guide Specification for Mass
Concrete," requires that a minimum capacity for batching,
mixing, and placing system be inserted. The determination
of the plant capacity is a part of the preparation of the
concrete materials DM, and the capacity inserted in the
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57. EM 1110-2-2000
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specification should be supported by the DM. Chapter 3 of
this manual gives additional guidance.
(3) Preset mixtures. If an automatic batching system is
required, it is necessary to indicate the number of present
mixtures that may be produced by the plant. This number
should be based on the anticipated construction sequence
and the number of different mixtures to be used in the
various features of the projects at approximately the same
time. For example, on a large dam it is likely that exterior
and interior mass concrete will be placed at the same time
but in different locations. It is also possible that structural
concrete may be required during the same shift as mass
concrete is being placed elsewhere. The number selected
should be realistic, not excessive simply to avoid the needed
planning and analysis.
(4) Mixers. Any type of stationary mixer may be used
for mixing concrete containing 75- or 150-mm (3- or 6-in.)
nominal maximum size aggregate if it meets the capacity
and the uniformity requirements. Concrete containing
50-mm (2-in.) and smaller maximum size aggregate may be
mixed in stationary or truck mixers.
n. Conveying and placing.
(1) Conveyance methods. Optional paragraphs are
provided to cover belt conveyors and pump placement, and
these should be included in the project specifications, or not,
depending on the project. The concrete materials DM
should be referred to when preparing the specifications
paragraphs related to methods of conveyance.
(2) Hot-weather mixing and placing. To reduce the
problems of slump loss and plastic shrinkage cracking,
limits are placed on the temperature of the concrete when
placed. For guidance in selecting the correct placing
temperatures, see Table 8-1 of this manual.
(3) Placing temperature. An optional paragraph of
CW-03305 requires a special placing temperature in certain
portions of the structure. The selection of an alternate and
the completion of the blanks within the paragraph chosen
shall be based on and supported by the concrete materials
DM or a separate DM on Thermal Studies as outlined in
Chapter 3 of this manual.
(4) Lift thickness. Lift thicknesses are to be shown on
the drawing which shall show the required and optional
construction joints. The maximum lift height for each
portion of the structure will be determined by the thermal
study and documented in the appropriate DM.
(5) Placing concrete in unformed curved sections. This
optional paragraph will be included in all specifications for
projects that include an ogee spillway crest and spillway
bucket.
(6) Concrete deposited in water. This optional
paragraph will be included in all specifications for projects
that include underwater placement concrete. The decision
to use underwater placement in lieu of conventional
dewatering must be discussed in the concrete materials
design memorandum as outlined in Chapter 2 of this
document.
o. Finishing.
(1) Unformed surfaces. A steel-trowel finish may be
specified for those areas requiring it by listing the areas in
the paragraph entitled "Trowel Finish" of the guide
specifications. Steel-trowel finishes are generally required
in areas where cleaning is required such as generator decks,
visitor facilities, and shop and office areas. If the floors are
to be overlaid with tile, coatings, or coverings, the
manufacturer’s recommendations should be consulted when
preparing the specifications to determine the finish
requirements.
(2) Formed surfaces. The guide specification provides
for four classes of finish for formed surfaces. The required
class of finish must be denoted on the project plans. An
AHV (Class A, high velocity) finish will be required on all
surfaces exposed to water velocities of 40 ft/s or higher.
(3) Insulation and special protection. These paragraphs
of CW-03305 contain blanks for cold-weather protection.
The information inserted in these paragraphs will be based
on and supported by the thermal study. It is also necessary
to determine the age beyond which insulation will no longer
be required. In areas where concrete placement is subject
to a winter shutdown, it should be assumed that all mass
concrete placed since the spring startup will be insulated
throughout the following winter shutdown period unless
results of the thermal study indicate otherwise.
p. Areas to be painted. If the project includes large
areas of concrete surfaces that will be painted, they should
be impervious-sheet cured, moist cured, or cured with a
chlorinated-rubber base curing compound.
q. Setting of base plates and bearing plates. The
paragraph with this title in CW-03305 with subparagraphs
should be included in the project specifications if the project
includes base plates or bearing plates. A gas-liberating
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58. EM 1110-2-2000
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admixture should be used only when the area is essentially
confined.
r. Measurement and payment. The paragraph entitled
"Measurement and Payment," CW-03305, will be edited to
reflect the outcome of the cementitious materials
investigation outlined in Chapter 2 of this EM and
documented in the concrete materials DM.
5-5. Guide Specification "Formwork for Concrete,"
CW-03101
a. General. The Guide Specification CW-03101,
"Formwork for Concrete," will normally be included in any
specification for a project which includes concrete in any
amount. It is included as "related work specified elsewhere"
in each of the three guide specifications for conventionally
placed concrete, CW-03307, CW-03301, and CW-03305.
Guidance for preparation of the project specifications is
included in the following paragraphs.
b. Shop drawings. The number of days that drawings
shall be submitted prior to fabrication should be based on
consultation with construction division personnel in the
district to determine a reasonable time.
c. Sample panels. Sample panels are required any time
a Class A or a special architectural finish is required.
d. Forms. The areas on the project to receive each
class of finish will be listed in the specification paragraph
entitled "Materials" of CW-03101. This information must
be taken from structural and architectural drawings.
e. Form removal. Forms will not be removed until a
specified length of time has elapsed and a percentage of the
concrete strength has been reached. The percentage figure
to be inserted must be obtained from the structural designer.
5-6. Guide Specification "Expansion,
Contraction, and Construction Joints in
Concrete," CW-03150
a. General. This guide specification should be included
in any project specification that includes joints in the
concrete.
b. Cost of testing. Preparation of a project specification
based on this guide specification requires that a division
laboratory be contacted and costs obtained for testing field-
molded sealants and nonmetallic waterstop. These costs are
inserted in specification CW-03150.
5-7. Guide Specification "Precast-Prestressed
Concrete," CW-03425
a. General. This Guide Specification CW-03425,
"Precast-Prestressed Concrete," is for use on important
structures which use precast-prestressed members; therefore,
it is not intended to be edited except to select available
options. Guidance for the section of the options is provided
in the following paragraphs.
b. Air content. The decision of whether or not to
require entrained air in precast members must be made
based on a determination of the exposure conditions to
which the members will be subjected both in service and in
transit and storage. Generally, air entrainment should be
required in any precast concrete placed in exposed locations
where freezing of concrete saturated with water is likely to
occur. When this decision is made, the optional paragraphs
in the guide specification will be edited accordingly.
c. Tolerances. The optional tolerance paragraphs will
be edited depending on the type of members being procured
by including or excluding those paragraphs which apply to
that type of member.
d. Cement. Guidance for selecting the various optional
requirements is provided in paragraph 2-2 of this manual.
e. Aggregates. The option is provided if using
aggregates meeting the requirements of ASTM C 33
(CRD-C 133) or if economically beneficial and technically
acceptable, the specifications of a state or local agency may
be used. This would be the case if, for example, the most
likely source of precast members was heavily involved in
producing units for a large highway department project and
had produced large quantities of aggregate for that purpose.
If the material was shown by case history or by testing to be
adequate for the need, advantage should be taken of the
availability and the resultant savings rather than forcing
production of an aggregate meeting a different specification
but offering no real advantage in concrete quality.
f. Finishing. Optional requirements are provided for
the type of finish depending on architectural or service
needs.
5-8. Guide Specification "Preplaced-Aggregate
Concrete," CW-03362
Preplaced-aggregate concrete is produced by placing a gap-
graded coarse aggregate in a form and later injecting a sand-
cement-fly ash grout to fill the voids. Its main advantage is
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59. EM 1110-2-2000
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its low volume change because of the high coarse aggregate
content and the point-to-point contact of the coarse
aggregate particles. See paragraph 11-2 of this manual for
more information.
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60. EM 1110-2-2000
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Chapter 6
Coordination Between Design and Field
Activities
6-1. Bidability, Constructibility, and Operability
Review
a. General. The requirements for bidability,
constructibility, and operability (BCO) reviews are outlined
in ER 415-1-11, "Bidability, Constructibility, and
Operability." BCO reviews are to be performed first during
the review period for the concrete materials DM and again
at least 30 days before formal advertisement for bids of a
construction contract. When concrete construction is
involved, it is important to assure that qualified personnel
from the area office or resident office are included in this
review process.
b. Review guidance. Some of the areas that the
personnel in the area or resident office provide important
input for concrete construction to the designers are:
(1) Recommend location of aggregate production or
handling facilities on or near the project site to avoid
conflict with future project construction activities.
(2) Recommend location of batch plant on, or near,
the project site for maximum efficiency and ease of concrete
delivery and placement.
(3) Recommend types of placing equipment to be and
not to be used.
(4) Present special forming and staging requirements.
(5) Recommend potential water sources.
(6) Recommend location of construction joints.
(7) Clarify bidding documents.
(8) Identify potential placement problem areas related
to the structural shapes, size, and location of reinforcement,
location of embedded items, conduits, blockouts, etc.
(9) Submit effects of proposed architectural
requirements upon constructibility.
(10) Submit effects on the construction schedule of
insulation requirements, concrete mixtures which develop
strength slowly, or other unusual design requirements.
6-2. Engineering Considerations and Instructions
for Construction Field Personnel
a. General. Subsequent to the award of any
construction which involves concrete features, a report
should be prepared by the designer outlining all special
engineering considerations and design assumptions and
providing instructions to aid the field personnel in the
supervision and quality verification of the construction
contract. The information provided will, for the most part,
summarize the data contained in the DM’s and include all
required formal discussions on why specific aggregate
sources, plant locations, structural designs, etc. were selected
so that the construction personnel in the field will be
provided the necessary insight and background needed to
perform reviews of the Contractor’s various submittal
proposals and to resolve construction conflicts without
compromising the intent of the design. This information
must not conflict with the project specifications and must
not contain any request to change these requirements. In all
cases, the contract specification will govern.
b. Content. A typical outline for the concrete
construction part of the report is provided as an aid in
preparing the engineering considerations and instruction for
construction field personnel:
I. Introduction
A. Purpose
B. Scope
II. Cementitious Materials Requirements or
Properties
A. General
B. Availability
III. Aggregate Requirements or Properties
A. General
B. Basis for selection of listed requirements
C. Possible processing requirements
D. Quality assurance testing
IV. Other Materials
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A. Chemical admixtures
B. Water
(1) Mixing
(2) Curing
V. Concrete Qualities Required at Various
Locations Within the Structures
VI. Concrete Temperature-Control Requirements
VII. Cold-Weather Concrete Requirements
A. Insulation
B. Time length of protection
VIII. Hot-Weather Concrete Requirements
IX. Contractor Quality Control and Government
Quality Assurance
X. Critical Concrete Placement Requirements
XI. Architectural Requirements
XII. Finish Requirements
c. Discussion by outline heading.
(1) Introduction. The purpose of the report will be
stated here and will also contain a statement on the scope of
the engineering considerations and instructions for
construction field personnel. Types of concrete and the
areas each type is to be placed are to be discussed.
(2) Cementitious materials requirements or properties.
All those cementitious materials that have been included as
options in the project should be discussed. If any type or
types of cementitious material may not be used, the basis
for the exclusion must be discussed to provide the
construction personnel on the site the information required
to correctly comment on the Contractor’s submittals and
proposed substitution of an unacceptable cementitious
material. All quality assurance testing requirements should
be discussed, including the required or desired frequency of
onsite sampling.
(3) Aggregate requirements or properties. All the
important characteristics of the selected aggregate sources
are to be summarized along with the basis for rejection of
any nearby aggregate sources that were investigated and
found to be unsuitable. Other helpful information to be
included would be an assessment of potential processing
requirements. Potential processing requirements that are to
be discussed are requirements for spray bars and sand
classifiers, requirements to make up a naturally deficient
fine or coarse aggregate size, removal of organic material,
and processing because of an excess of elongated particles
by a roll crusher should be noted if the processibility studies
have revealed such. The range of aggregate quantity
parameters derived from testing of the listed sources must
be provided to the field so that the results of the quality
assurance and quality control tests during construction can
be compared to the assumed design values. It is especially
important to note the qualities that are critical and those
qualities that are marginal for acceptability of any source.
A list of the quality assurance tests to be performed by the
Government and the desired frequency of testing is to be
included.
(4) Other materials.
(a) Chemical admixtures. The reasons for allowing or
disallowing the use of retarding, accelerating, water-
reducing, high-range water-reducing, or any other commonly
used chemical admixture must be stated.
(b) Water. It must be noted if the concrete materials
investigations have shown any problems with the available
sources of mixing and curing water, such as a tendency to
stain the concrete or seasonable variations that would be
objectionable.
(5) Concrete qualities required at various locations
within the structures. The most important objective of the
report is to provide to the construction personnel in the field
the quality (type) of concrete required for each structure or
specific portion of a structure. Depending upon the nature
of the construction project, this information could be
presented in tabular form or by color coding the appropriate
project drawings. The quality should be designated by
maximum w/c, nominal maximum aggregate size, strength
requirement, and purpose, such as interior mass, exterior
mass, interior structural, exterior structural, backfill,
architectural, etc. It should be noted that for isolated
congested areas the nominal maximum aggregate size must
be reduced. The basis for the quality requirements, i.e.
strength, durability, appearance, etc., is to be stated for each
one listed. The age at which the compressive strength, f′c ,
is to be attained should be noted. Other mixture
proportioning requirements which are to be listed are the
nominal maximum size aggregate, air content, and the slump
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62. EM 1110-2-2000
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range. It should be noted that the concrete should be
sampled and tested for air, slump, and compressive strength
during plant shakedown so that any necessary adjustments
to the laboratory mixture proportions can be made before
concrete is placed in the structure. It should also be noted
that sampling for mixture proportioning should be observed
by project office personnel to assure that quality and grading
meet the specifications.
(6) Concrete temperature-control requirements. If
temperature-control requirements are a part of the project
specifications, they are to be explained in the report. To the
maximum extent possible, this discussion should describe
the effects of any changes in the proportioned mixtures upon
the thermal control measures for the project as well as the
results of any changes from the anticipated construction
schedule. If more extensive temperature- control measures
are specified, such as postcooling or postwarming, they are
to be described in sufficient detail to allow for timely
review of the Contractor’s submittals for these systems.
The most common methods of temperature control involve
specified maximum or minimum placing temperature,
followed by the use of insulation. Some possible methods
that the Contractor may submit to achieve the specified
placing temperatures are to be discussed along with any
known methods that have been unsuccessful in the past.
(7) Cold-weather concrete requirements. Assumed
methods of achieving the specified results during cold
weather are to be discussed in this report. Any specified
concretes in the project that require cold-weather protection
in excess of that to ensure freedom from damage of early
freezing is to be explained. The use of any specific
accelerators, the keeping of temperature records, heating of
materials, foundation preparation, protective insulating
coverings, heated enclosures, curing, and form removal are
to be discussed.
(8) Hot-weather concrete requirements. The assumed
methods of achieving the specified results during periods of
hot weather are to be discussed in this report.
(9) Contractor quality control and government quality
assurance. Contractor quality control (CQC) requirements
are specified in the specification. Government quality
assurance (GQA) sampling and testing requirements should
be discussed. These may include, but not be limited to,
sampling and testing frequency, sampling size and
procedures, testing methods, and analysis of test results for
cementitious materials, aggregate grading, aggregate
moisture, aggregate quality, slump, air content, concrete
temperature, and compressive strength.
(10) Critical concrete placement requirements. All
areas of the project that the designer feels require special
measures during placement, consolidation, finishing, or
curing are to be discussed in this report. Some examples
are the placement of trunion girders, tunnel linings, bridge
decks, and areas subjected to high-velocity flows of water.
(11) Architectural requirements. All areas where the
specified architectural requirements will affect the concrete
placement are to be discussed in this report. This will
include all areas where the location of construction joints is
mandatory for the desired aesthetic results or where exposed
aggregate or form linings are required. The report should
supplement the project specifications by providing
information on possible techniques to achieve the desired
surface textures and explaining the effects the architect
wants in the facility.
(12) Finish requirements. The type of finish, as
detailed on the drawing for each portion of the structure, is
to be discussed.
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63. EM 1110-2-2000
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Chapter 7
Preparation for Construction
7-1. Materials Acceptance Testing
a. General. Depending on the nature of the project
and the guide specification selected, acceptance of the
concrete materials proposed for use on a project will be
based on testing in a government laboratory, certified test
results, or certificates of compliance submitted by the
Contractor. An important responsibility of the resident
engineer’s staff is to assure that materials submitted for
testing or that certificates of compliance represent the actual
materials proposed for use.
b. Cement, pozzolan, and GGBF slag. The
requirements for the acceptance testing of cement, pozzolan,
and GGBF slag are stated in the various guide specifications
for concrete. The policy and responsibilities for carrying
out the cement, pozzolan, and GGBF slag acceptance testing
function of the Corps of Engineers is set forth in
ER 1110-1-2002, "Cement, Pozzolan, and Slag Acceptance
Testing." The procedures for requesting cement, pozzolan,
and GGBF slag testing and the procedures for sampling and
testing are outlined in the ER. The USAEWES is
responsible for the sampling, testing, and quality verification
of cement, pozzolan, and GGBF slag at mill or source
locations within the Continental United States (CONUS).
Personnel at the district, area, or residency level are
responsible for requesting cement, pozzolan, and GGBF slag
acceptance testing, determining the amount of the charges,
and providing the required funding document to WES.
Residency personnel remain responsible for assuring that the
cement, pozzolan, and GGBF slag reaching the project site
are from sources that have been tested, have not been
contaminated in transit, and are properly handled and stored
at the project site. When cement or pozzolan is supplied
from sealed bins, the members of the residency staff are
responsible for sampling, shipping the samples to WES, and
sealing the bins and transporting vehicles. For additional
information contact CEWES-SC. When cement, pozzolan,
and GGBF slag are being supplied from a prequalified
source, project samples will be taken and funding to WES
provided as outlined in ER 1110-1-2002. Project personnel
should sample at the frequency required or may choose to
sample more frequently if they suspect that the cement,
pozzolan, or slag may be deviating from the specification
requirements. There is no additional charge for testing
project samples when these samples are taken to aid in
assessing a problem with the material being delivered to the
project. When cementitious materials are accepted by mill
tests, this requirement should be strictly enforced, and a file
of the mill test reports should be maintained. Silica fume
will be accepted by certified test reports from the
manufacturer.
c. Chemical admixtures. The procedures for
acceptance testing of chemical admixtures for concrete are
outlined in ASTM C 260, ASTM C 494, and ASTM D 98
(CRD-C 13, 87, and 505, respectively). When acceptance
testing is required by the project specifications, sampling
will be performed by resident office personnel, and testing
will be performed by a division laboratory. To reduce
duplication of effort, results of completed tests of chemical
admixtures should be routinely furnished to WES in
accordance with ER 1110-1-8100, "Laboratory
Investigations and Materials Testing."
(1) Test of air-entraining admixtures. The procedures
for testing air-entraining admixtures are covered in ASTM C
233 (CRD-C 12), and the specifications for air-entraining
admixtures are given in ASTM C 260 (CRD-C 13).
(a) Abbreviated tests. When it has been determined
by review of previous data obtained from quality tests that
a division laboratory has a sufficient background of
information on a given air-entraining admixture to indicate
that it is a product of good quality and acceptability as
determined by the criteria set forth in ASTM C 260,
subsequent samples may be evaluated by abbreviated tests.
Abbreviated tests shall consist of performing all tests called
for under regular tests except those for determination of
compressive and flexural strength at 28 days, 6 months, and
1 year, and resistance to freezing and thawing. Tests to
determine compliance with the time-of-setting requirements
need not be performed unless specially requested.
(b) Initial uniformity tests. On the first sample of air-
entraining admixture tested for a project and found to
comply with the applicable requirements by either the
quality tests of ASTM C 260 or by the abbreviated tests,
initial uniformity tests will be conducted to provide criteria
for evaluation of results of uniformity tests on samples
representing subsequent lots. The uniformity tests will
consist of pH, density, and air content of mortar as outlined
in ASTM C 233.
(c) Uniformity tests of subsequent samples. Samples
representing a subsequent lot of air-entraining admixture
from the same source on the same project as a previous lot
tested by quality or abbreviated tests and found to comply
with the applicable requirements may be tested by the
uniformity test methods outlined in ASTM C 233. The
results of uniformity tests will be compared with the results
of the initial uniformity tests, and if they agree, the air-
entraining admixture may be considered to comply with the
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64. EM 1110-2-2000
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specifications. Rejection of the air-entraining admixture
should be based only on full or abbreviated test results.
(2) Test of other chemical admixtures. The
specifications and procedures for testing and evaluating
chemical admixtures are given in ASTM C 494 and ASTM
C 1017 (CRD-C 87 and 88).
(a) Abbreviated tests. When it has been determined
by review of previous data obtained from quality tests that
a division laboratory has sufficient background of
information on a given admixture to indicate that it is a
product of good quality and complies with the specifications
set forth in ASTM C 494, subsequent samples may be
evaluated by abbreviated tests. Abbreviated tests of
chemical admixtures shall consist of two rounds of tests for
water content, initial time of setting, and compressive
strengths at 3, 7, and 28 days.
(b) Initial uniformity tests. On the first sample of
admixture tested for a project and complying with the
applicable requirements by either the quality tests of
ASTM C 494 or by the abbreviated test, initial uniformity
tests will be made to provide criteria for evaluation of
results of uniformity tests on samples representing
subsequent lots. The uniformity tests will consist of density,
residue by oven drying, and infrared spectroscopy.
(c) Uniformity test of subsequent samples. Samples
representing a subsequent lot of admixture from the same
source on the same project as a previous lot tested by
quality or abbreviated tests and found to comply with the
applicable requirements may be tested by the uniformity test
methods outlined in ASTM C 494. The results of these
uniformity tests will be compared with the results of the
initial uniformity tests, and if they agree, the admixture may
be considered to comply with the specifications. Rejection
of the admixture should be based on full or abbreviated
tests.
(3) Tests of accelerators. If calcium chloride is used
on a project using the minor concrete guide specifications,
it may be accepted based on recent certification that it
complies with ASTM D 98 (CRD-C 505) or ASTM C 494,
Type C or E.
d. Aggregates - listed source. When the Contractor
proposes to furnish aggregates from a listed source, the
resident engineer remains responsible for assuring that the
aggregate being produced is of similar quality to that which
was tested during the design process. Immediately after
receipt of information on the Contractor’s source of
aggregates, samples should be taken from material produced
by the Contractor and forwarded to a division laboratory for
a confirmation of quality. The amount of testing to be
conducted will vary with each individual source. Testing
program considerations will include length of time since
testing was last performed, the amount of material removed
from the source since testing was performed, and the
variability of the deposit. The resident office should
correlate testing requirements with the engineering division
materials engineer. The Contractor on mass concrete
projects using guide specification CW-03305 will have
responsibility for quality testing before mixture
proportioning samples are taken.
e. Aggregates - nonlisted source. When the
Contractor proposes to furnish aggregates from a source not
listed in the specifications, samples will be taken by the
Contractor under the supervision of the resident office. The
methods of sampling are outlined in CRD-C 100. The
approval or disapproval of the proposed source should be
handled as quickly as possible, and appropriate personnel
from the division and district should make site visits as
needed when a major project is involved. The evaluation of
test results is primarily a responsibility of the engineering
division of the district or division office. The source will be
accepted only if the quality meets the required test limits.
The aggregate samples will be tested and evaluated in
accordance with the guidance provided in Chapter 2 of this
manual. All testing will be accomplished in the appropriate
division laboratory.
f. Aggregates - minor concrete jobs. Minor concrete
job specifications will require the aggregate to meet
ASTM C 33 (CRD-C 133) or a state highway specification.
If the concrete supplier’s source of aggregate is from a local
source which has been used for some time, then a service
record will have been established and only minimum testing
is necessary. The resident engineer or project engineer,
however, has the responsibility to ascertain that the
aggregates meet the required quality, and if there is any
question, such as a newly opened source, quality testing
should be performed in the division laboratory.
7-2. Mixture Proportioning
a. For concrete projects using Guide Specification
CW-03305, mixture proportioning is the responsibility of the
Government. Before the concrete placing starts, the mixture
proportioning study should be completed using materials
proposed by the Contractor. Chapter 4 of this manual
discusses in detail the procedures for sampling of concrete
materials for mixture proportioning and for proportioning to
meet project requirements. The mixture proportioning
criteria are to be provided to project personnel as outlined
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65. EM 1110-2-2000
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in Chapter 6. The importance of submitting samples which
meet quality and grading requirements and which are
representative of materials to be supplied to the project can-
not be overstated. Due to the variation of materials supplied
during construction, mixture proportions may need to be
adjusted. Adjustment of laboratory mixture proportions
should be done during plant shakedown.
b. For projects using Guide Specification CW-03301,
the mixture proportioning is the responsibility of the Con-
tractor. Before the concrete placing starts, the Contractor
should submit the mixture proportions and all the test
reports for review.
c. For structures using Guide Specification
CW-03307, the concrete will most likely be supplied by
local ready-mixed plants. The Contractor’s mixture
proportions should be submitted to the resident office and
should be checked for appropriateness and completeness
before start of concrete production.
7-3. Concrete Plant and Materials
a. Review of concrete plant drawings. The contract
specifications may require the Contractor to submit drawings
showing the layout and material handling details of the pro-
posed concrete plant to the Contracting Officer for review.
It is the Contractor’s responsibility to provide and maintain
a dependable concrete plant of the required capacity.
Review comments should be limited to (1) if the plant meets
the requirements of the contract specifications or (2) a list
of specific deficiencies if the plant does not meet the speci-
fied requirements and (3) any other comments on specific
plant features or details that are questionable or appear
deficient.
b. Estimating plant capacity. The capacity of a
concrete plant is commonly determined by the number of
mixers, the rated capacity of each mixer, along with the
charging, mixing, and discharging time of each mixer. The
total time required should be increased by 15 sec/batch
when the capacity for sustained operation is computed.
Thus, a concrete plant that contains two 4-yd3
tilting drum
mixers, each of which can be charged in 20 sec and
discharged in 15 sec, would have the following computed
capacity: A "rule of thumb" mixing time for a 4-yd3
, one-
opening, tilting-type mixer is 1 min, 45 sec. Therefore, the
total time per 4-yd3
batch for such a mixer is:
20 sec - charging mixer
1 min, 45 sec - mixing
15 sec - discharging
15 sec - other
______________________
2 min, 35 sec - Total
Thus, the concrete plant capacity is 8 yd3
in 2 min, 35 sec
or approximately 185 yd3
/hr. If the number of mixers is
insufficient when judged by the mixing time calculation,
which may be the case if the Contractor proposes to use
turbine mixers or very large tilting mixers, the plant should
be designed so that the extra mixers can be added. Any
comments on the concrete plant should point out that the
extra mixer(s) will be required if the mixing time proposed
by the Contractor does not satisfy the uniformity
requirements. Normally, batching time is not critical.
However, in a plant equipped with a vertical shaft (turbine)
mixer, in which cumulative weighing is employed, the
batching cycle should be compared to the mixing cycle to
determine which is critical. It is always necessary to make
a careful check of the capacity of the material conveying
systems into the concrete plant and the concrete
transportation system from the concrete plant to the
placement site. When placing concrete in the area of the
structure that is the most remote from the concrete plant, the
concrete transportation system should be capable of handling
the entire output of the plant with allowances made for any
time required to reposition the discharge equipment and
minor delays by the placing crew.
c. Aggregate storage, reclaiming, washing, and
rescreening. Most project specifications for any size project
will require that sufficient aggregate be on the site to permit
the continuous placement and completion of any lift started.
The contractor’s proposed plant for the storage and delivery
to and from storage should be checked to determine if they
are of sufficient capacity to be able to easily comply with
the production capacity requirements. The capacity of the
storage bins should be checked against the preliminary mix-
ture proportions to assure adequate size for all mixes. If the
fine aggregate is wet when it is stockpiled and there are no
mechanical dewatering devices provided, there must be
sufficient storage capacity to allow the fine aggregate to
drain freely to obtain a uniform and stable moisture content
before being deposited in the batch plant bin. Aggregate re-
claiming facilities, washing, and rescreening facilities (when
required) should be carefully examined to determine that
they are of sufficient capacity to maintain all of the bins
over the batchers at least half full when the plant is pro-
ducing concrete at the rated maximum capacity of the plant.
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66. EM 1110-2-2000
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d. Concrete cooling plant capacity. There are two
principal requirements of an aggregate cooling system:
(1) there must be sufficient refrigeration capacity, and
(2) the aggregate must be in contact with cooling system
long enough to permit the transfer of sufficient heat between
the aggregate and the medium. The refrigeration capacity
must be that required for the maximum placing rate during
the hottest summer months with an assumed loss of at least
10 percent between cooling and mixing. The length of time
required for the heat transfer will depend upon the aggregate
size. For example, if 150-mm (6-in.) aggregate is exposed
to ice water for 20 min, less than 85 percent of the potential
cooling will be accomplished regardless of the size of the
refrigeration plant. The aggregate handling facilities should
be planned so that heat gain is minimized after cooling.
Modern ice-making equipment that can handle ice efficiently
is available so that, for saturated aggregates, all the added
water can be in the form of ice. It is important that all ice
melts prior to the conclusion of mixing. Liquid nitrogen is
also extensively used for cooling concrete, especially when
the nitrogen manufacturing facilities are within the
geographic area. Liquid nitrogen can be sprayed directly
into the mixer with no ill effect. The nitrogen must be
added while the mixer is turning. ACI 207.4R and the PCA
"Design and Control of Concrete Mixtures" (Kosmatka and
Panarese 1988) are excellent references for more detailed
study.
7-4. Batching and Mixing Equipment
a. Checking compliance with specification
requirements. Prior to the beginning of concreting
operations, the plant should be checked for compliance with
the specification requirements. During the erection of the
plant and installation of the equipment on large jobs, the
inspection staff should become thoroughly familiar with the
plant and its operating features. Plant drawings submitted
by the Contractor for review by the Contracting Officer
should be used in making the check and in becoming
familiar with the plant.
b. Scale checks. All scales should be checked by
standard weights before being placed in operation. During
plant shakedown and the beginning of concrete production
for onsite plants, the operation of the scales should be
observed closely. If any trouble is apparent, it should be
corrected immediately. Subsequently, the accuracy of the
scales should be checked once a month. Checking of scales
is a responsibility of the Contractor under the quality control
provisions, but the government inspection force has the
responsibility for verification. This verification should be
accomplished by observation of the scale checks performed
by the Contractor and actually checking scales when an
accuracy disagreement occurs.
c. Mixer blades and paddles. Mixer blades should
be examined before concrete production begins and must be
monitored during construction. If there is a buildup of
hardened concrete in the drum or if the blades become badly
worn, previously obtained uniformity test data are no longer
applicable. Thus, when the blade shows 10-percent wear,
the blades should be replaced and additional uniformity tests
run. Several methods have been used to monitor blade wear
to determine when the blade has worn 10 percent. One
method is making a plywood template of portions of the
blades. Another is drilling small holes in the blade where
"10-percent wear" would be. Another is simple blade
measurements. Measurements or holes must be located and
recorded so that they can be relocated. Selection of method
and monitoring must begin at the time the uniformity test is
performed. Pug mill paddles should be checked in a similar
manner.
d. Recorders. The agreement between recorder
reading and dial indications should be checked regularly.
This can be done easily whenever scales are calibrated,
although it may be done any time the scales are in
operation. The pens on pen recorders should be examined
frequently to ensure that they are not clogged, that they have
a supply of ink, and that they do not produce too wide a
line. It is a source of convenience to write on the chart the
location at which concrete is being placed at any time.
e. Batching sequence. When aggregates are batched
cumulatively, the last material batched has its mass recorded
with the least accuracy since the tolerances in project
specifications apply to the total mass in the hopper rather
than to the mass of the individual fraction. If possible, fine
aggregate should not be batched first or last. It should be
batched second, following the coarse aggregate fraction
having the smallest mass. Batching sequence can have a
profound effect on mixing time for most mixers. If a
charging conveyor is used, then ribboning materials together
on the belt as much as possible can result in more efficient
mixing and shorter mixing time. Liquid admixtures should
be batched with the water or damp sand. Each chemical
admixture should be batched separately and should be
batched at the same point in the charging cycle for every
batch.
f. Mixer performance and mixing time. The mixing
time at the start of a job using onsite plant mixers should be
determined prior to the start of concrete production. On
jobs covered by Guide Specification CW-03305, mixer
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67. EM 1110-2-2000
1 Feb 94
performance tests will be conducted by the Contractor as
required by the specifications. The mixer performance tests
for plant mixers are performed in accordance with
CRD-C 55 at the specified intervals. The mixer
performance tests for plant mixers using continuous mixers
are to be performed in accordance with CRD-C 55 with the
spacing of the sampling intervals modified as appropriate for
the continuous operation. Allowable variation will be the
same as for batch mixers. When truck mixers are in use on
any size job, their performance will be determined at the
specified intervals in accordance with ASTM C 94 (CRD-C
31) and shall meet the variation tolerance specified therein.
When mobile volumetric batching and continuous mixing
plants are used for minor structures, mixer performance tests
shall be performed in accordance with and shall meet the
variation tolerance specified in ASTM C 685 (CRD-C 98).
When plant mixers are used, tests at reduced mixing times
will be made by the Government any time reduced mixing
times are proposed by the Contractor. Tests may be
conducted by the Government at the initial startup of the
plant for mass-concrete jobs if desired.
7-5. Conveying Concrete
a. General. Transportation of concrete from the
mixer to the forms should be done as rapidly as possible so
that the properties of the concrete as discharged from the
mixer are not changed materially. The devices used for
receiving the concrete from the mixers and conveying it to
and depositing it in the forms should be designed to
maintain the concrete in the same condition in which it is
discharged from the mixer. ACI 304R provides an easily
obtainable source of information on transporting concrete.
The contractor’s conveying system should be reviewed and
appropriate comments provided.
b. Buckets. When concrete is transported from mixer
to forms in bottom-dump buckets, controllable discharge
buckets are required. The specifications limit the size of the
pile in which concrete may be deposited to 4 yd3
. However,
buckets with a capacity greater than 4 yd3
may be used if
they have multiple discharge gates or other controls so that
more than one pile is deposited on discharge, none of which
exceeds 4 yd3
.
c. Truck mixers and agitators. Truck mixers will not
adequately mix concrete made with aggregate having a
maximum nominal maximum size greater than 37.5 mm
(1-1/2 in.) and should not be used for mixing or transporting
and agitating such concrete or concrete with 2-in. slump or
less. In general, whenever truck mixers are permitted for
mixing concrete, agitators may be used for hauling concrete
in the event the contractor elects to use centrally mixed
concrete, except that agitators will not be used when it is
necessary to delay mixing of the batched material until the
truck has arrived at the construction site. This requirement
may occur when the batching, conveying, mixing, and
placing operations would require more time than allowed by
the specifications or when the rate of placement is so slow
or intermittent that mixing cannot be properly scheduled at
the central mixing plant. In such situations, a procedure of
batching all the materials except cement, and not more than
80 percent of the water at the batch plant, and transporting
to the construction site where the cement and remaining
water is batched and the concrete mixed, should be used.
d. Nonagitating equipment. Truck-mounted
nonagitating equipment specifically designed for hauling
concrete may be used for a haul requiring less than 15 min
over a smooth road. Standard dump trucks should never be
used to haul conventional concrete.
e. Positive-displacement pump. The transportation of
concrete through pipelines by positive-displacement pumps
is an acceptable method for transporting concrete of medium
consistency. This method is especially useful for tunnel
linings and other areas with insufficient room for handling
buckets. Pumps may be authorized whenever the aggregate
size, slump, and length of line are within the manufacturer’s
recommendations for the apparatus proposed and the desired
quality of concrete can be obtained. A positive-
displacement pump is a piston pump or a squeeze pressure
pump. A pneumatic pump is not a positive-displacement
pump. The use of aluminum for concrete pump pipe is not
permitted. The use of aluminum pipe is potentially
dangerous and could result in substantial reduction in the
strength of the concrete. Refer to ACI 304.2R for more
information on placing concrete by pumping methods.
f. Belts. Slow conveyor belts are unacceptable as
standard practice for transporting concrete. This method
tends to produce segregation as the concrete travels on a
slow belt. Any belt traveling at less than 300 ft/min is con-
sidered slow. When making the decision on whether or not
to permit the use of conveyor belts to transport concrete,
residency or area personnel should refer to ACI 304.4R
which includes information on parameters and specifications
for belt placement. Regardless of the outcome of the analy-
sis of the contractor’s proposal, the use of a belt conveyor
should be discontinued if excessive segregation results.
g. Chutes. Chutes which are supplied by the ready-
mixed truck manufacturer as a normal part of the ready-
mixed trucks are usually satisfactory. Most other chutes
tend to segregate the concrete as it is discharged and should
not be approved.
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68. EM 1110-2-2000
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7-6. Preparation for Placing
a. General. Placing of concrete should not be
permitted until preparations have been completed.
Preparation for placing includes form construction, cleanup
of surfaces, assembling of placing and protection equipment,
and other operations essential to proper concreting
operations.
b. Earth foundations. Earth foundations should be
properly compacted and should be clean and damp prior to
placing the concrete.
c. Rock foundations. Rock foundations should be
thoroughly cleaned and given any other necessary treatment
required to ensure proper bond of the concrete to the rock.
Roughening by "bush hammering" or by sandblasting may
be necessary on certain types of rock; however, the removal
of all loose coatings, scale, drummy rock, dried grout, and
other similar materials usually provides a surface of required
roughness.
d. Cleanup of concrete surfaces. Construction joints
in concrete to which other concrete is to be bonded must be
thoroughly cleaned to remove laitance and other harmful
coating. When properly prepared, the surface of the
concrete will present only clean coarse aggregate surfaces
and sound mortar. Roughness is not necessarily a
requirement. Cleanup of construction joints is usually
accomplished by either one of three methods or by the use
of a combination of these methods. These are the air-water
cutting (green-cut), high-pressure water jet, and sandblasting
methods. Some job specifications contain an optional
provision, which if invoked, makes it possible for the
Contractor to use a surface-applied retarder to extend the
period of time during which air-water cutting is effective.
When the Contractor elects to use a surface retarder, he is
required to submit a sample for approval and to demonstrate
the method of application. The surface retarder should meet
the requirements of CRD-C 94. The principal requirement
to be met by the application procedure is that it supply a
uniform coat in all kinds of weather. Without retardation,
the use of the air-water method requires particular care if
satisfactory results are to be obtained. The time at which
the air-water cutting should be accomplished is critical and
is materially influenced by prevailing temperature
conditions. When properly timed, the surface can be
cleaned so that laitance resulting from bleeding is removed.
Frequently, the proper timing of the operations on the entire
surface of a lift in a large dam is not achieved and this
probability should be considered before the method is
approved. Cutting too early by the air-water or high-
pressure water jet method results in damage to the surface
by undercutting the large aggregate and in the removal and
wasting of otherwise suitable concrete. Cutting too late
results in failure to clean the surface properly and
necessitates wet sandblasting. A pressure of 3,000 psi
appears to be adequate for cleaning concrete by the high-
pressure water jet for concrete with strength of 3,000 psi.
Higher strength concrete may require a pressure up to as
much as 6,000 psi. Trials should be conducted on project
concrete to establish the correct pressure. Cleaning by the
sandblast method is accomplished after the surface has
hardened and should be delayed as long as practicable,
preferably until just prior to placing the next lift. The
Contractor will be required to provide means for handling
the disposal of the joint cleanup waste so that exposed
surfaces will not be stained or otherwise damaged. Light
sandblasting to remove surface stains resulting from faulty
cleanup operations or the use of unsuitable curing water is
permissible, but it will not be necessary if the cleanup
operations are properly executed. The best bond between
lifts is obtained when the surface of the old concrete is
neither bone dry nor saturated but has been saturated and is
in a drying condition.
e. Placing equipment. The requirements for placing
equipment vary widely from job to job, depending on the
plant used and placing conditions. The necessary facilities
should be reviewed in advance and provided ready for use.
In reviewing, attention should be given to the following
specific items.
(1) Vibrators. Vibrators should comply with
specification requirements. A sufficient number of vibrators
should be at the job site to permit placing. Also there
should be a reasonable number of spare vibrators available.
(2) Cold-weather and hot-weather protection
equipment. Devices and methods proposed by the
Contractor must meet the specifications requirements for
cold-weather and hot-weather concreting. The equipment
should be examined for adequacy and applicability well in
advance of winter concreting so that any deficiencies may
be corrected by the Contractor. Refer to ACI 305R and
ACI 306R for more information on hot-weather and cold-
weather concreting.
(3) Communication equipment. The Contractor
should provide equipment for his use between the forms and
mixing plant. The need for other equipment such as
signaling and identifying devices depends on the complexity
of the project and the number of different concrete mixtures
employed. The resident engineer should require the
Contractor to present for review plans or descriptions of the
equipment well in advance of the start of concrete
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69. EM 1110-2-2000
1 Feb 94
placement. The GQA representative should be provided
with separate communication equipment between the forms
and mixing plant on large jobs where the mixture
proportions are provided by the Government.
(4) Other equipment. The need for additional
equipment depends on job requirements. Such equipment
includes wire brooms for spreading grout, water removal
equipment, elephant trunks, etc.
f. Forms. The type of forms to be used by the
Contractor will be submitted for approval prior to
construction. The submittal should be checked for
compliance with the specifications.
g. Curing and protection. The methods and
equipment proposed by the Contractor for the curing and
protection of concrete should be reviewed to assure that they
are capable of curing the concrete and protecting it in
compliance with the specifications. Follow-up inspections
should assure that the approved materials and equipment for
curing and protection are available at the project site prior
to the beginning of concrete placement.
h. Approval. Concrete placing should never begin
until approval to do so by the Government has been given.
A form checkout record should be used for larger and more
complex projects. The record should include form line and
grade, grout tightness of the form, proper size numbers and
position of reinforcement, waterstops, mechanical or
electrical lines, cleanup of foundation or previous lift, proper
transportation, placing and vibrating equipment, and curing
and protection equipment. Both the government quality
verifier and the Contractor’s foreman should sign or initial
the record. Figure 7-1 is a sample of a form checkout
record.
i. Interim slabs on grade. Unless there is some other
overriding reason, interior slabs on grade should be
underlain by a capillary water barrier consisting of 4 to 6 in.
of open-graded granular material, preferably crushed rock.
While some engineers consider a vapor barrier unnecessary,
it is usually good practice to install a vapor barrier below
the concrete slab and above the capillary water barriers.
This consists of a continuous plastic sheet, 6 mil or more
thick. In some parts of the country, particularly the
Southwest, it is customary to cover the vapor barrier with
2 in. of sand because of the concern that, without the
separator, warping of the slab would be intensified. While
in other parts of the country the vapor barrier is customarily
placed directly beneath the concrete slab without a sand
separator, it would be conservative practice to use the sand
separator unless previous experience shows no need for it.
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70. EM 1110-2-2000
1 Feb 94
FORM CHECKOUT
I T E M
INSPECTED BY APPROVED BY
CONTRACTOR CORPS OF ENGINEERS
NAME DATE TIME NAME DATE TIME
GEOLOGY FOUNDATION
DRAINAGE
CROSS SECTION
FORMS
LINE & GRADE CONTROL
CONCRETE PLACING
REINFORCING
PIPING
WATER STOP
ANCHOR BOLTS
MISC. MECHANICAL
ELECTRICAL
CLEANUP
SAFETY REQUIREMENTS
WEATHER PROTECTION
VIBRATING EQUIPMENT
CURING MATERIALS
F I N A L C L E A R A N C E
CONTRACTOR REPRS: C.O.E. REPRS:
I N S T R U C T I O N S
CONCRETE PLACING SHALL NOT BEGIN UNTIL EVERY ITEM IS CHECKED AND THE FINAL CLEARANCE IS SIGNED.
IF ANY ITEM IS NOT APPLICABLE, IT SHALL BE NOTED "NA" AND SIGNED.
BEFORE APPROVING THE "SAFETY REQUIREMENTS" ITEM, A FINAL INSPECTION SHALL BE MADE OF ALL WORKING FACILITIES FOR CONCRETE
PLACING SUCH AS SCAFFOLDS, LADDERS, PLATFORMS, ACCESS WAYS, ETC., TO ASSURE THAT THEY ARE ADEQUATE, SAFELY CONSTRUCTED,
AND IN READINESS.
FINAL CLEARANCE SUBJECT TO REVOCATION IF SUBSEQUENT INSPECTION REVEALS ANY DEFICIENCIES.
IF SUMMONED BY THE CONTRACTOR TO CHECK AN ITEM AND IT IS FOUND TO BE UNSATISFACTORY, STATE IN THE "REMARKS" COLUMN THE
TIME SUMMONED AND THE TIME REJECTED.
Figure 7-1. Example of form checkout record
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71. EM 1110-2-2000
1 Feb 94
Chapter 8
Concrete Construction
8-1. Forms
a. Types of materials. The contract specifications
specify the types of finish required for the various formed
surfaces and the types of materials permitted for each class
of finish. If more than one type of material is permitted
with each class of finish specified, the Contractor should
always be permitted to employ his choice of materials.
b. Quality verification. After concrete forms have
been set to line and grade and prior to permitting any
concrete to be placed therein, the forms should be carefully
inspected for compliance with all specification requirements,
including sheathing materials, alignment of form surfaces,
mortar tightness, and apparent strength.
c. Form coating. Most of the form coatings
commercially available are satisfactory for wood forms.
Quite frequently, form coatings which are satisfactory for
wood forms do not perform satisfactorily on steel forms. If
the form coating being used on the work is unsatisfactory,
its use should be immediately discontinued and the
Contractor should be required to obtain a suitable form
coating.
8-2. Placing
a. General. The practices followed in the placement
of concrete should have the principal objectives of concrete
that is bonded to the foundation or to the previous lift,
uniform in quality, free from any objectionable segregation,
and thoroughly consolidated. These objectives are best
accomplished by adequately cleaning and preparing the top
surface of the foundation or the previously completed lift,
delivering the freshly mixed concrete to its approximate
final position in the structure with a minimum of
segregation, and consolidating the concrete by means of
sufficient vibration to consolidate it completely. In addition
to these very general practices, the more detailed practices
outlined below should be followed.
b. Bedding mortar on rock foundations. All rock
foundations should be covered with a layer of mortar just
prior to concrete placement. The mortar should be
composed of the same fine aggregate and cementitious
material used in the exposed concrete mixture. The
sand/cementitious material and w/c of the mortar should also
be the same as that used in the exterior concrete mixture
proportions. Addition of an air-entraining admixture is not
required. The thickness of the mortar layer should be
approximately 1/4 in. The delivery and spreading of the
mortar should be scheduled so that all mortar is covered by
the concrete before the initial set of the mortar.
c. Mass concrete. The general nature of mass
concrete, having a stiff and dry consistency and containing
75- and 150-mm (3- and 6-in.) maximum size aggregates,
is such that the concrete must be deposited in the final
position in the structure in which it is to remain when
compacted. The quantity of interior mass concrete that can
be properly compacted in one operation is recognized to be
about 4 yd3
. The project specifications will usually limit the
amount to be deposited in one pile for compaction to 4 yd3
in uncongested areas and to smaller quantities in congested
areas. Depositing 8 yd3
in two contiguous piles from a two-
compartment (4-yd3
each) bucket is recognized to be in
compliance with this requirement. Whenever the top of a
lift is not horizontal, the placement must proceed up the
slope. The thickness of the exterior concrete in a mass
concrete structure is governed by the size of the bucket or
the delivery equipment used in placing the concrete. Since
the project specifications will limit the amount of concrete
that may be deposited in one pile to 4 yd3
, the exterior
concrete will usually average about 5 to 6 ft thick. The
placing procedure to be followed includes practices designed
to keep the thickness of the exterior mixture to a practical
minimum. Usually, a 7-1/2-ft lift of mass concrete is placed
in five layers, and a 5-ft lift of mass concrete is placed in
three layers as shown in Figures 3-1 and 3-2 of this manual.
For example, in dam construction, if both interior and
exterior mass concrete are used, the placement should begin
with the first layer of interior mass concrete at the upstream
end of the placement, leaving a space of the minimum
practical, or specified, width between the interior mass
concrete and the form for the placement of the exterior
mixture concrete. The exterior mass concrete layer should
be placed after the corresponding interior concrete layer has
been placed, so as to keep the thickness of the exterior
concrete to a practical minimum, or that specified. The
intersection of the interior and exterior concretes should be
carefully consolidated and "knit" together during vibration.
The placement should then proceed toward the downstream
face with the bottom layer preceding the second layer by an
approximate distance equivalent to 4 yd3
of concrete
compacted. Each successive layer above should follow the
layer below by approximately the same distance, thus
providing a stepped placing procedure. The placement
should follow a regular sequence for the successive layers
by maintaining the stepped relationship of the layers until
the lift is completed. Dumping of concrete on slopes and
chasing it downhill with vibrators is not to be permitted
under any circumstances. The transporting of concrete by
vibration is not permitted.
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72. EM 1110-2-2000
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d. Structural concrete. Proper care must be taken to
avoid segregation when placing concrete into structural units
such as walls, columns, slabs, beams, etc. The concrete is
to be deposited in approximately its final position in the
structure where it is to remain and should not be moved
within the forms with vibrators. As a general rule, when the
concrete bucket cannot be lowered to within 5 ft of the
position where the concrete is to be placed, elephant trunks
with a rigid drop chute bottom section are to be used. All
belt conveyors must have elephant trunks at their discharge
ends. The thickness of the layers should not exceed 20 in.
The vibrators should be handled carefully so that thorough
consolidation is achieved without damaging the forms or
displacing embedded items. The vibrator should not be
operated while being held against the form which results in
sandy streaks or markings in the finished surface.
e. Tunnel linings.
(1) Inverts. The concrete for tunnel inverts may be
delivered to the placement site by any practical means. It
should be brought to grade in layers not to exceed
approximately 1-1/2 ft and thoroughly consolidated with
vibrators.
(2) Sidewalls and crown. Use of a positive
displacement pump is the normal method of placing the
concrete in tunnel linings. In the tunnel sidewalls, the
concrete should be placed in successive layers of
approximately 1-1/2 ft deep and thoroughly consolidated by
vibration. In the crown of the tunnel where vibration is
impossible, a length of the special pipeline used in the
concrete pumping operation is kept buried in the fresh
concrete. This is necessary to achieve consolidation of the
concrete and to force the concrete into the overbreaks in the
rock. Placement of the concrete in the crown must begin at
the end of the form that is opposite the concrete pump, and
the embedded pipeline will be backed out as the crown is
filled. Short sections of vertical riser pipes have been used
satisfactorily, in lieu of the buried pipeline, to place concrete
in the tunnel crown. Pumping concrete is discussed in
paragraph 10-6 of this manual and in ACI 304.2R.
f. Consolidation. Concrete that is placed in the dry
with conventional methods should be consolidated by means
of mechanical vibration equipment. The performance of the
vibrators used by the Contractor should be periodically
checked for compliance with the performance characteristics
required by the contract specifications. Vibrators should
never be used to transport the fresh concrete within the
forms. The duration of vibration at a single point in the
fresh concrete being consolidated should be approximately
10 to 15 sec or until the entrapped air is released, which is
indicated when large air bubbles stop coming to the top of
the mixture near the insertion point of the vibrator. It is
essential that the points of vibration be fairly closely spaced
to obtain thorough and complete consolidation of fresh
concrete. Proper care must be exercised to thoroughly
vibrate the concrete in all forms, including flowing concrete,
to minimize rock pockets, honeycomb, and other defects.
It is almost impossible to over vibrate a properly
proportioned concrete mixture. Emphasis should be placed
on having closely spaced applications of appropriate
duration rather than prolonged vibration at widely spaced
distances. The latter method will result in inadequate
consolidation in some parts of the concrete, which will
result in an overall general reduction in the quality of the
hardened concrete. In general, the use of internal vibrators
for consolidation of freshly mixed concrete has been
satisfactory. A thorough discussion of consolidation is
given in ACI 309R.
g. Protection of waterstops. There are many cases of
leakage through a joint because of faulty installation of the
waterstop. To eliminate such failures, particular care must
be exercised to ensure that waterstops are properly protected
and installed. Adequate provisions must be made to support
and protect all waterstops against damage during the
progress of the work. Extraordinary care must be employed
in the placement and consolidation of the concrete adjacent
to the waterstops to ensure that the waterstops are not
damaged and that they are in the correct position and
properly embedded in the concrete.
8-3. Finishing
a. Formed surfaces. The finishing of concrete
structures consists of dressing up the formed surfaces by
patching the form bolt holes and removing any defective
concrete and replacing it with sound durable concrete. This
latter operation can be largely avoided by paying particular
and vigilant attention to the details of the concrete
placement operations, especially the consolidation, so that
defective concrete will not occur. When such conditions do
occur on exposed surfaces, the defective concrete must be
chipped back to sound concrete and replaced by dry packing
or a conventional concrete placement. In the removal of the
defective concrete, care should be taken to prevent
damaging the adjacent concrete while creating a dovetail or
key into the hardened concrete to firmly anchor the new
repair concrete. All defective concrete on the surface of a
structure that is permanently exposed to view should be
repaired. Additional guidance on repair materials and
methods may be found in EM 1110-2-2002, "Evaluation and
Repair of Concrete Structures." Honeycomb and rock
pockets on bulkhead faces usually do not need to be
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73. EM 1110-2-2000
1 Feb 94
repaired unless they are of considerable extent or depth.
Extra care must be taken to assure that the color and texture
of the repair concrete closely matches that of the
surrounding concrete. The guide specifications are clear and
detailed in their requirements for all formed surfaces. The
key to quality is the strict enforcement of the specification
requirements. Class A finish is the best finish with the most
strict requirements, while Class D is the least restrictive.
Class AHV is a special finish for spillways, tunnels, or other
water passages where the velocity of the water is expected
to be 40 ft/s or higher. The materials and workmanship for
forming of Class AHV are the same as the Class A finish
requirements in Guide Specification CW-03101, "Formwork
for Concrete," except that steel forms may be used. The
allowance for offsets for Class AHV is more restrictive.
b. Unformed surfaces. The finishing of unformed
surfaces is a very critical operation and requires the use of
judgment, experience, and skill to produce a finished surface
of the specified quality and durability. Crazing, scaling, and
other defects are usually directly attributable to the use of
concrete which is too wet (too high a slump), improper
finishing procedures, or a combination of both.
Overworking the surface is probably the most common
cause of defective surface finishes. The fresh concrete
should be thoroughly consolidated. The surface of the
consolidated concrete should be slightly above grade.
Screeding, or strikeoff, should be done immediately after
consolidation. The screeding operation, when accomplished
by hand methods, is to be accomplished with a sawing
motion of the screed in the transverse direction to the line
of travel of the screed. This will accomplish the dual
purpose of screeding and compacting the surface at the same
time. Any excess concrete that is left above grade should
be carried ahead of the screed. In a properly proportioned
air-entrained concrete, a characteristic roll of fresh concrete
will form in front of the screed. In air-entrained concrete
which has been properly consolidated, a slight rebound of
the fresh concrete will occur behind the screed. Screeding
should be limited to two passes of the screed. After the
second pass of the screed, the rebound will be diminished
to a negligible amount. Floating or darbying should be
completed immediately after screeding and should be limited
to that necessary to fill in low spots. The use of a jitterbug
or tamper to embed the coarse aggregate particles should not
be allowed. Floating and troweling should not be permitted
on any part of the surface where any bleed water has
collected. This bleed water must either be allowed to
evaporate or be removed in a satisfactory manner. Dry
cement, or a mixture of cement and fine sand, should never
be applied directly to a surface to be finished for the
removal of bleed water or for any other purpose. Adding
water to the surface by use of a large brush, or other means,
should also be prohibited. The use of power rotary
troweling machines needs to be carefully controlled to
prevent overfinishing and the resultant crazing.
(1) Ogee crest. One of the most difficult finishing
jobs on unformed surfaces is the ogee crest of a spillway.
The following procedure is the most satisfactory one
developed to date. The spillway piers and the high-strength
erosion-resistant concrete in the spillway surface are placed
monolithically with the spillway except for the top lift,
which includes the ogee crest. Adjustable vertical rigid
supports, conforming to the ogee shape are installed in the
placement, raising the depth of the screed above the finished
grade and bridging the placement surface. Concrete is
placed and consolidated in the usual manner and then
screeded and finished using the pipe as an elevation guide.
When these operations are properly executed, a durable
surface is produced.
(2) Spillway aprons. No general rules can be given
for finishing of spillway aprons or stilling basin slabs.
Since the shapes required to meet the hydraulic requirements
differ for different projects, it is usually necessary to
develop special methods for each situation. The finishing is
frequently done by hand, although properly designed heavy-
duty mechanical screeding equipment is acceptable. The
method described above for ogee crests is suitable, with
appropriate modifications, to the finishing of stilling basins,
the curved transition surfaces at the toe of a dam, or for flip
bucket spillways.
(3) Trapezoidal channel lining. The methods to be
used on bottom slabs are the same as for any flat or nearly
flat slab. The concrete should be placed and consolidated
in the usual manner and left slightly above grade. The slab
should then be struck off to grade by screeding and given a
float finish. Finishing the sideslope paving in small
channels will usually be accomplished by hand methods.
Placing of the concrete will proceed upslope. The concrete
should be of medium to dry consistency. The use of a
mechanical screeding machine is considered advisable.
Hand-manipulated screeds which are moved by mechanical
means can also be used. Screeding should always proceed
upslope. After screeding, the surface should be given a
float finish.
(4) Surfaces exposed to high-velocity flow of water.
Surfaces to be exposed to waterflow velocities greater than
40 ft/s should be finished carefully (AHV finish) since any
discontinuity especially a positive offset in downstream
direction in the surface can be the cause of cavitation.
Cavitation has the potential of seriously eroding concrete
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74. EM 1110-2-2000
1 Feb 94
surfaces so the finishing of areas subject to cavitation
damage should be carefully inspected.
(5) Floors.
(a) Monolithic. Where monolithic floors are specified,
the completion of the floors should be delayed, if possible,
until all other construction work from which damage to the
floor might occur is completed. If this is impracticable, the
floor should be adequately protected from damage.
(b) Bonded topping. In areas where structural slabs
must be completed for the work to be accomplished, bonded
or "two-course" floors are usually selected so that the final
finish can be delayed until all other work is virtually
complete. This eliminates the necessity for special
protection; however, the rough slab should be protected
against spillage of liquids or other materials which might
later interfere with bonding of the floor topping. The
surface of the base slab should be prepared for the topping
in the same manner as the surface of any horizontal
construction joint.
c. Tolerance requirements for surface finish.
(1) General. Control of surface tolerance may be
critical in some types of structures such as warehouse
guideway surfaces and surfaces subject to high-velocity flow
(over 40 ft/s). There are two approaches in controlling the
floor surface tolerance; using straightedge (or curved
templates for curved surfaces) or measuring the F numbers
in accordance with ASTM E 1155 (CRD-C 641). Both
approaches are used in Corps of Engineers (CE)
specifications depending upon the type of structures.
(2) Control surface tolerance by straightedge. This is
the traditional method for measuring surface tolerance. The
tolerance is defined as the maximum gap between a fixed
length straightedge and the concrete surface at any point.
The device is simple, portable, and easy to use. There will
be no calculation or data collection. This procedure can be
used on any surface; horizontal, vertical, overhead, even
curved surface (by using a curved template). However,
there are some limitations on this approach. The
measurements are arbitrary, subjective, and generally
nonrepeatable. There is no mention of the number of
measurements to be made and therefore it totally depends on
the operator. The difficulty in enforcing the requirement
using this method often results in controversies between
owners and contractors. This procedure is specified for
mass-concrete structures and minor concrete structures and
may be specified as an option in cast-in-place concrete
structures in CE civil works projects. For mass-concrete
structures, the requirement of surface tolerance falls into two
extremes. The surface tolerances for most mass-concrete
structures, such as surfaces of a dam or floors of a lock
chamber or gallery, are less critical where tight control is
not necessary. Although a 10-ft straightedge has been
commonly used in the industry, a 5-ft straightedge is
specified for mass concrete due to the difficulty in handling
the 10-ft straightedge on surfaces other than floors. On the
other extreme, the surface subject to high-velocity water
flow requires extreme tight control in surface tolerance to
reduce the possibility of cavitation and erosion. A special
surface class (Class AHV) has been created for this purpose.
The straightedge or curved template is specified in this case
since most of the surfaces involved are either vertical,
overhead, or curved where the F-number system cannot be
used. For minor concrete structures where a small quantity
of concrete is used, the control of surface tolerance is less
critical. The use of the F-number system in these structures
is not necessary.
(3) Control floor tolerance by F-number system. In
1987 ASTM issued a standard test procedure, ASTM E
1155, for measuring floor surface profiles and for estimating
the characteristic flatness and levelness of a floor. This
procedure measures elevations at regular intervals along
straight lines on the surface. The differences in elevations
between adjacent points and between all points 10 ft apart
are then calculated. The results of these calculations are
analyzed statistically to obtain floor flatness number (FF)
and floor levelness number (FL). Floor flatness is defined as
the degree to which a surface approximates a plane while
levelness is defined as the degree to which a surface
parallels horizontal. These two numbers represent the
average quality of floor finish in a predefined area and are
reliable and repeatable. It should be noted that there is no
direct correlation between straightedge tolerances and
F-numbers. However, based on the effort required to finish
a floor to the corresponding tolerance, Table 8-1 provides a
rough correlation between the two systems. The F-number
system may be specified as an option for all cast-in-place
concrete floors for consistency with industry standards and
practices. Currently, the construction technology can
achieve FF 25 at little or no additional cost. Therefore, for
normal slab or floor construction, FF should be at least 25.
FL should be used for slab on grade only, since the levelness
of an elevated floor is beyond the control of the Contractor
due to camber and deflection of supporting system. In some
cases, it may be necessary to specify localized FF/FL in
addition to the overall FF/FL to assure a uniform floor
quality. Details and concept of the F-number system are
available in ACI 302.1R, ACI 117R commentary, and
ASTM E 1155.
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75. EM 1110-2-2000
1 Feb 94
Table 8-1
Floor Quality as Determined by
F-Number System and Straightedge
F-Number
Gap Under an Unleveled
5-ft Straightedge, in.
Gap Under an Unleveled 10-ft Straightedge,
in.
Bull floated FF 12 3/8 1/2
Straightedged FF 20 1/4 5/16
Flat FF 32 1/8 3/16
Very flat FF 50 1/16 1/8
8-4. Curing
a. General. Early hydration proceeds at an
acceptable rate only if the concrete is maintained at a high
humidity. Thus, positive curing procedures are essential,
especially for thin sections. Even in massive sections, the
quality of the surface concrete is dependent upon adequate
curing. The Contractor should present his plans for curing
for approval well before concreting begins. During
construction, these operations must be continually checked.
Form curing, where no additional moisture is added, is not
an acceptable method of curing. Where forms are left in
place during curing, the forms should be kept wet at all
times.
b. Moist curing. Proposed methods of keeping
concrete surfaces continually moist by spray-pipe or fog
systems, soaker hoses, ponding, or covering with damp
earth, saturated sand, or burlap maintained in a damp
condition in contact with the concrete are satisfactory.
Plastic, aluminum, galvanized, or alloy pipe should be
required to avoid rust stains on the concrete surfaces. Hand
sprinkling is not satisfactory and should not be permitted
except as an emergency measure. Water that will stain the
concrete should not be approved unless it is not practical to
furnish a nonstaining water. The Contractor should be
required to clean surfaces permanently exposed to view if he
uses water that stains.
c. Membrane curing. Areas cured by pigmented
membrane-forming coring compounds are relatively easy to
inspect and should be specified wherever possible. Uneven
distribution of the compound is readily revealed by a
nonuniform appearance. In those areas in which a
nonpigmented compound is required such as surfaces to be
exposed to view, a government quality verifier should be on
hand during all spraying operations and should check
closely the uniformity of the application. In a hot, dry
environment, the energy from the direct sunlight may raise
the surface temperature significantly which will promote
formation of shrinkage cracks on the surface. Therefore,
when using nonpigmented curing compound, it is required
that shading should be provided for 3 days whenever the
maximum ambient temperature during that period is
expected to be higher than 90 °F. Compressed air lines
must have traps to prevent moisture or oil from
contaminating the compound. Ordinary garden hand-spray
outfits are not satisfactory and should not be permitted.
Application by brushing or rolling should not be permitted.
Pigmented compounds should be thoroughly mixed in the
receiving containers by the insertion of a compressed air
pipe into and near the bottom of the container prior to
withdrawing the material for use. Continuity of the
membrane coating must be maintained for the duration of
the full specified curing period. The membrane should be
protected by suitable means if traffic thereon is unavoidable.
Any damage to the membrane during the curing period
should be immediately repaired at the original specified rate
of coverage. Additional information may be found in
ACI 308.
d. Sheet curing. Sheet curing is an acceptable curing
method, although it is not often used except for curing slabs.
Some of the materials used are easily torn by equipment or
by wind, and constant inspection and maintenance is
required. It is important that very secure tiedowns or heavy
objects be used with this system to maintain a sealed
environment for curing the concrete. Polyethylene film is
easily torn and tends to leave a pattern on the surface where
the film wrinkles. Maintenance of the film during the
curing period is a constant problem due to wind and
construction activity. Inspection requires constant scrutiny.
It is not allowed except for smaller jobs.
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76. EM 1110-2-2000
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8-5. Cold-Weather Concreting
a. General. Cold weather is defined by ACI 306R as
a period of three or more consecutive days when the
average daily ambient temperature is less than 40 °F, and
the ambient temperature is not greater than 50 °F for more
than one-half of any 24-hr period. The average daily air
temperature is the average of the highest and the lowest
temperatures occurring during the period from midnight to
midnight. The objectives of cold-weather concreting
practices are to:
• Prevent damage to concrete due to freezing at early
ages.
• Assure that the concrete develops the required
strength for safe removal of forms, shores, and reshores and
for safe loading of the structure during and after
construction.
• Maintain curing conditions which foster normal
strength development without using excessive heat and
without causing critical saturation of the concrete at the end
of the protection period.
• Limit rapid temperature changes, particularly before
the concrete has developed sufficient strength to withstand
induced thermal stresses.
• Provide protection consistent with the intended
serviceability of the structure.
Proper cold-weather concreting practices and procedures are
based on the principles that:
• Concrete that is protected from freezing until it has
attained a compressive strength of at least 500 psi will not
be damaged by a single freezing cycle.
• Where a specified concrete strength must be attained
in a few days or weeks, protection at temperatures above
50 °F is required.
• Little or no external supply of moisture is required
when concrete is properly protected and sealed during cold
weather except within heated protective enclosures.
b. Planning. Proper planning by the contractor to
protect fresh concrete from freezing and to maintain
temperatures above the required minimum values should be
made well before the freezing temperatures are expected to
occur. Equipment and materials required to protect concrete
from freezing should be at the job site before cold weather
is likely to occur, not after the concrete is placed and its
temperature begins to approach the freezing point. All
surfaces that will be in contact with newly placed concrete
should be at temperatures that cannot cause early freezing
or seriously prolong setting time of the concrete.
Ordinarily, the temperatures of these contact surfaces,
including subgrade materials, need not be higher than a few
degrees above freezing.
c. Protection system. ACI 306R provides guidance
on minimum concrete placing temperatures and on the
maintenance duration of these temperatures. The actual
temperature at the concrete surface determines the
effectiveness of protection, regardless of the ambient
temperature. Therefore, monitoring concrete temperatures
at several locations along the concrete surface, particularly
at corners and edges, is important. As noted in
paragraph 4-2d of this manual, concrete should not be
exposed to cycles of freezing and thawing while in a
critically saturated condition until it has attained a
compressive strength of approximately 3,500 psi. The
specific protection system required to maintain concrete
temperatures above freezing depends on such factors as the
ambient weather conditions, the geometry of the structure,
and the mixture proportions. In some cases, covering the
concrete with insulating materials to conserve the heat of
hydration may be all the protection that is necessary.
Insulation must be kept in close contact with the concrete or
the form surface to be effective. Some commonly used
insulating materials include polystyrene foam sheets,
urethane foam, foamed vinyl blankets, mineral wool, or
cellulose fibers, straw, and commercial blanket or batt
insulation. In more extreme cases, i.e. ambient temperatures
less than -5 °F, it may be necessary to build enclosures and
use heating units to maintain the desired temperatures. Heat
can be supplied to enclosures by live steam, forced hot air,
or combination heaters of various types. Although steam
provides an excellent curing environment, it may offer less
than ideal working conditions and can cause icing problems
around the perimeter of the enclosure. Heaters and ducts
should be positioned not to cause areas of overheating or
drying of the concrete surface. Combustion heaters should
be vented for safety to prevent reaction of carbon dioxide in
the exhaust gases with the exposed surfaces of newly placed
concrete.
d. Curing. Concrete exposed to cold weather is not
likely to dry at an undesirable rate unless the protection
which is selected for use increases the likelihood of rapid
drying. Measures should be taken to prevent drying when
concrete is warmer than 60 °F and exposed to air at 50 °F
or higher. Either steam or a liquid membrane-forming
curing compound should be used to retard moisture loss
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77. EM 1110-2-2000
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from the concrete. Water curing should not be used since
it increases the likelihood of concrete freezing in a critically
saturated condition when protection is removed.
e. Accelerating early strength. Accelerating
admixtures, Type III portland cement, or additional cement
can be used to shorten the times needed to achieve setting
and required strength if proper precautions are taken.
Reduction in time of setting and acceleration of strength
gain may permit shorter protection periods, faster reuse of
forms, earlier removal of shores, or less labor in finishing
of flatwork. The acceleration of strength development of
mass concrete should not be allowed since doing so will
tend to increase internal temperature rise of the concrete. A
more thorough discussion of all topics related to cold
weather concreting is given in ACI 306R.
8-6. Hot-Weather Concreting
a. General. ACI 305R defines hot weather as any
combination of the following conditions that tend to impair
the quality of freshly mixed or hardened concrete by
accelerating the rate of moisture loss and rate of cement
hydration, or otherwise resulting in detrimental results:
• High ambient temperature.
• Low relative humidity.
• Wind velocity.
Hot weather may lead to concrete mixing, placing, and
curing problems which adversely affect its properties and
serviceability. Most of these problems relate to the
increased rate of cement hydration at higher temperature and
the increased evaporation rate of moisture from the freshly
mixed concrete. Detrimental effects of hot weather on
freshly mixed concrete may include increases in: water
demand, rate of slump loss, rate of setting, tendency for
plastic shrinkage, and difficulty in controlling air content.
Hardened concrete may potentially experience decreased 28-
day and later age strengths, increased tendency for drying
shrinkage, and differential thermal cracking, decreased
durability resulting from cracking, increased permeability,
and greater variability of surface appearance. In addition,
proper temperature control of mass concrete may be more
difficult to achieve during hot weather.
b. Planning. Damage to concrete caused by hot
weather can never be fully alleviated, and so good judgment
is necessary to select the most appropriate compromise of
quality, economy, and practicability. The type of
construction, characteristics of the concrete materials, and
the hot-weather concreting experience of the Contractor all
affect the procedures used to minimize potential problems.
Lack of hot-weather concreting experience by the
Contractor’s personnel usually causes the most difficulties
in achieving concrete of the required quality. Early
preventative measures should be applied with the emphasis
on materials evaluation, advanced planning, and
coordination of all phases of the work. Detailed procedures
for mixing, placing, protecting, curing, temperature
monitoring, and testing of concrete during hot weather
should be submitted by the Contractor prior to the beginning
of hot-weather concreting. The potential for thermal
cracking, either from overall volume changes or from
internal restraint, should be anticipated. Items that should
be considered to control cracking include limits on concrete
temperature, cement content, heat of hydration of cement,
form-stripping time, selection and dosage rate or quantity of
chemical admixtures and pozzolans, joint spacing, and use
of increased amounts of reinforcing steel.
c. Alleviating measures. Practices and measures
which will help to reduce or avoid the potential problems of
hot-weather concreting include:
• Using concrete materials and proportions with
satisfactory records in field use under hot weather
conditions.
• Using cooled concrete. For general types of
construction in hot weather, it is not practical to recommend
a maximum limiting ambient or concrete temperature
because circumstances vary widely. Therefore, ACI 305R
recommends that, if possible, a practical maximum concrete
temperature of between approximately 75 and 100 °F be
determined. This should be done by testing laboratory trial
batches of concrete which are produced at the selected
limiting temperature or at expected job site high
temperature. For projects using CW 03305, "Mass
Concrete," the maximum placing temperature for concrete
in the massive features should be determined by a thermal
study. For all other concrete, the maximum placing
temperature should be as shown in Table 8-2, which relates
maximum concrete temperature to relative humidity.
• Using a concrete consistency that permits rapid
placement and effective consolidation.
• Transporting, placing, consolidating, and finishing
the concrete with the least delay.
• Scheduling placing operations during times of the
day or night when weather conditions are favorable.
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78. EM 1110-2-2000
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Table 8-2
Maximum Placing Temperature
Average Annual
Relative Humidity, %
Maximum Concrete
Temperature, °F, at Placement
>60 90
40-60 85
<40 80
NOTE: If the period that the concrete placements may occur can be anticipated, then the Weather Service Office in the project area should
be asked to supply an average monthly relative humidity for that period.
• Protecting concrete against moisture loss at all times
during placing, finishing, and during its curing period.
d. Placing temperature. The problems of placing
concrete in hot weather involve, among other things, slump
loss during mixing and transporting and surface crazing after
placement. To reduce these problems, limits are placed on
the concrete placing temperature in the guide specifications.
The temperatures that are selected for inclusion in each
paragraph are dependent on the normal relative humidity in
the project area. The required maximum placing
temperature may be lower if required by thermal studies and
included in the appropriate DM.
e. Plastic-shrinkage cracks. Plastic-shrinkage
cracking is often associated with hot-weather concreting,
particularly in arid climates. It occurs primarily in flatwork,
but beams and footings are also susceptible if the
evaporation rate exceeds the rate of bleeding. Plastic-
shrinkage cracking is easily identified since it begins to
appear before the concrete completely hardens. The cracks
appear in a random pattern on the surface and are wide at
the surface, tapering to nothing at a shallow depth. The
cracks may be up to 1/4 in. (6 mm) wide at the surface and
seldom more than 4 to 6 in. (100 to 150 mm) deep. High
concrete temperatures, high ambient temperatures, high wind
velocity, and low relative humidity, alone or in combination,
cause rapid evaporation of water from the concrete surface
and significantly increase the probability of plastic-shrinkage
cracking. ACI 305R provides a graphical means for making
evaporation rate estimates based on all the major factors that
contribute to plastic-shrinkage cracking. A close
approximation of evaporation rate can also be made in the
field by evaporating water from a shallow pan of known
surface area. Initial and subsequent weighings made to the
nearest 0.1 g every 15 to 20 min allow the evaporation rate
to be calculated in a reasonably short period of time prior to
concrete placement. When the evaporation rate approaches
0.2 lb/ft2
/hr, precautions should be taken by the Contractor
to reduce moisture loss, or plastic-shrinkage cracking may
occur.
f. Effect on strength and durability. Concrete
material properties and the concrete mixture proportions
have a significant effect on both fresh and hardened
properties of concrete placed during hot weather. High
mixing water temperatures cause higher concrete
temperatures which, in turn, increase the amount of water
needed to achieve a given slump. If additional water is
added so that the w/c is increased, the strength and
durability of the concrete may be detrimentally affected. A
1-in. slump decrease may typically be expected for every
20 °F increase in concrete temperature. The increase in
water content necessary to maintain concrete slump in hot
weather will range between 2 and 4 percent depending on
the concrete temperature. This increase may be significantly
less if WRA or HRWRA is used. The use of a slower
setting Type II portland cement may help improve the
handling characteristics of concrete in hot weather; however,
concrete made with slower setting cements may be more
likely to exhibit plastic-shrinkage cracking. Because the
cement makes up only 5 to 15 percent of the mass of a
concrete mixture, its temperature has a relatively minor
effect on concrete temperature. An 8 °F increase in cement
temperature is typically required to increase concrete
temperature 1 °F. If the cement has a false set tendency,
slump loss may be aggravated in hot weather. Retarding
WRA and HRWRA have all been beneficial in offsetting
some of the undesirable effects of hot weather on concrete.
Admixtures without a performance history with the concrete
materials selected for the work should first be evaluated in
laboratory trial batches at the expected high temperature,
using procedures described in ACI 305R. Some HRWRA’s
may not demonstrate their potential benefits when used in
small laboratory batches. Further testing may then be
required in full-size batches. Since concrete contains a
relatively large mass of coarse aggregate, changes in its
temperature have a considerable effect on concrete
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79. EM 1110-2-2000
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temperatures. For example, a 1.5 to 2 °F coarse aggregate
temperature reduction will lower the concrete temperature
about 1 °F. Therefore, cooling coarse aggregate is a very
effective means of lowering concrete temperature.
g. Cooling. If limiting temperatures govern the
delivery of the concrete, the availability of cooled concrete
should be ascertained well in advance of the need. Cooling
of the concrete will require installation of special equipment
and assurance of an ample supply of cooling materials such
as ice or liquid nitrogen for the anticipated concrete volume
and placement rate. Maintaining a continuous flow of
cooled concrete to the placement is important to avoid the
possible development of cold joints. Arrangements should
be made for the ready availability of backup placing
equipment and vibrators in the event of mechanical
breakdowns. Arrangements should be made for ample water
supply at the site for wetting subgrades, fogging forms, and
for moist curing, if applicable. The fog nozzles used should
produce a fog blanket and should not be confused with
common garden-hose nozzles. Materials and means should
be on hand for erecting temporary windbreaks and shades as
needed to protect the concrete against drying winds and
direct sunlight. The materials and means for the curing
methods selected should be readily available at the site to
permit prompt protection of all exposed concrete surfaces
from drying upon completion of the placement.
h. Curing. Proper moist curing of concrete placed in
hot weather is the best curing method for assuring strength
development and minimizing drying shrinkage. It can be
provided by ponding, covering with prewetted burlap or
cotton mats, covering with clean sand kept continuously
moist, or continuous sprinkling. The use of a liquid
membrane-forming curing compound may be more
economical and practical than moist curing in many
instances. Properly applied pigmented membrane-forming
curing compounds provide good protection from direct
sunlight. On flatwork, application should be started
immediately after disappearance of the surface water sheen
after the final finishing operation. Forms should be covered
and kept continuously moist during the early curing period.
They should be loosened, as soon as practical without
damaging the concrete, and provisions made for curing
water to run down inside them. A thorough discussion of
curing and other topics related to hot-weather concreting is
given in ACI 305R.
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80. EM 1110-2-2000
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Chapter 9
Concrete Quality Verification and Testing
9-1. Quality Verification
a. General. The construction quality verification
system is necessary to assure the Government that the
finished work complies with the plans and specifications.
The inclusion of quality control requirements for the
Contractor does not relieve the Contracting Officer of the
responsibility for safeguarding the Government’s interest.
For civil works concrete construction, the resident engineer
has the added responsibility for obtaining the quality of
concrete in the various parts of the structure based on
explicit instruction from the engineering division of the
district office (see Chapter 6 of this manual). Depending on
the scope of the work and the guide specification selected,
the Government may or may not select the mixture
proportions, but in all cases, the Contracting Officer is
responsible for assuring that the strength and other
requirements as set forth in the specifications or in the
designer’s instructions to the field personnel are met. The
Contractor will mold, cure, and perform strength testing of
concrete cylinders as part of his quality control program.
The Government will perform compressive strength testing
as part of the quality assurance program. In case of arch
dams, all strength testing will be molded, cured, and
performed by the Government. The budget for these GQA
responsibilities should be included in the Project
Management Plan. Details of requirements and procedures
for CQC and GQA are specified in ER 1180-1-6,
"Construction Quality Management," which contains detailed
requirements for controlling projects with prescriptive
specifications such as the mass-concrete specification. The
GQA responsibility is not to be imposed on the construction
contractor. If personnel shortages preclude the use of
government personnel to accomplish GQA, it should be
done by a commercial testing organization under contract to
the Government.
b. Government quality assurance. During the
construction stage, the Contracting Officer, through his
authorized representatives, which include the resident
engineer and his staff, is responsible for acceptance testing
and quality verification to enforce all specification
requirements and for monitoring the Contractor’s quality
control operations. These functions include but are not
limited to: verification of all operations for compliance with
specifications, reviewing and, when required, approving
contractor submittals including certificates of compliance
and contractor-developed mixture proportions. If acceptance
testing of cement, pozzolan, slag, admixtures, or curing
compounds are required, the resident engineer is responsible
for making the necessary arrangements for such tests with
the appropriate division laboratory, or in the case of cement,
pozzolan or GGBF slag, with WES. The resident engineer
is responsible for requesting the division laboratory to verify
the quality of the government project laboratory, any
commercial laboratories operating under contract to the
Government and the contractor’s quality control laboratory
as required by ER 1110-1-261, "Quality Assurance of
Laboratory Testing Procedures."
(1) Quality assurance representative. This individual
may be a government employee or may be an employee of
a private engineering firm under contract to the Government
and not affiliated with the construction contractor. He is the
key figure in the operations attendant to concrete quality
assurance. The effectiveness of the quality verification
operation in assuring uniformity of the concrete and in
obtaining compliance with specification requirements
depends to a large degree on the thoroughness with which
the quality assurance representative is instructed and trained
in the performance of his duties. While it is expected that
the quality assurance representative will have knowledge of
the basic requirements for the production of concrete of high
quality, it is nevertheless necessary to instruct him in the
details of quality verification as they apply to each specific
project. This should be accomplished through training
conferences together with written guides and instructions
prepared by the government concrete engineer and his shift
supervisors or by the project engineer on smaller projects.
Previous experience on similar work is highly desirable.
Previous experience cannot entirely compensate, however,
for proper instruction and training of quality assurance
representatives in the duties unique to a particular project.
These representatives should be assigned to a project prior
to completion of the contractor’s concrete plant. Preferably,
they should be trained for duty on a particular project as the
concrete plant is being erected so that they may become
thoroughly familiar with the plant and particularly those
aspects of the equipment bearing on the quality verification
procedures. For example, on a large concrete project the
mixing plant quality assurance representative should become
familiar with the mixing plant and all of its operating
features. All persons assigned as quality assurance
representatives should be certified by ACI or have
equivalent training. EP 415-1-261 provides detailed
responsibilities and a check list for the GQA representative.
(2) Testing technicians. Technicians, either
government employees or employees of a private
engineering firm contracted by the Government, are
responsible for the quality assurance testing to verify the
Contractor’s quality control tests and for acceptance testing
of the concrete. They are also responsible for obtaining
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81. EM 1110-2-2000
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samples of materials for other laboratories. All work done
by technicians must be done in strict accordance with
applicable standards to ensure the validity and acceptance of
test results. Certification of concrete technicians is provided
by ACI. This certification can be obtained by completing
a 3- or 4-day course offered by ACI at announced times in
many of the major cities of the country or by completing the
Concrete Technicians Course at WES. All persons assigned
as concrete technicians and responsible for quality assurance
testing should be certified by ACI or have equivalent
training.
(3) Organization.
(a) General. The Government’s quality assurance
organization must be flexible to allow for changes in rates
of placement as construction progresses. In general, the
following organizations should be provided by the
Government to satisfy the area/resident engineer’s
responsibility for acceptance testing and quality verification
to enforce all specification requirements and for monitoring
the contractor’s quality-control operations.
(b) Major concrete project. On large concrete
projects, the organization should have a materials engineer
(or technician) reporting directly to the resident engineer and
being responsible for all phases of quality assurance from
aggregate production through curing and protection of the
concrete. The organization should include a shift supervisor
(quality assurance representative) for each shift. Under each
shift supervisor, the organization should include one placing
quality assurance representative for each location at which
concrete is being placed, one mixing plant quality assurance
representative, and one quality assurance representative
assigned to verification of cleanup, curing, protection, and
finishing. The organization should include a laboratory
technician and assistants as required to handle acceptance
testing of aggregates and concrete, to consolidate reports,
prepare summary reports, and keep records. The laboratory
technician should report directly to the materials engineer.
On a very large project, several contracts on the same
project may be supervised by a single area engineer. Under
such circumstances, the engineer reports to the resident
engineer and supervises all concrete activity on the project.
The quality assurance force required for aggregate quality
verification depends upon job conditions. Where the
Contractor’s quality control has been proven satisfactory,
sampling should be required only at the point of acceptance
(mixing plant) and the quality verification should consist
only of routine observation of plant operations; this work
can be handled jointly by the shift supervisors and the
engineers or by special assignment. Usually quality
verification of aggregate processing operations does not
require continuous assignment of personnel.
(c) Moderate concrete volume. For smaller projects,
it is necessary to modify the organization to suit the project
conditions. In most instances, quality assurance
representatives are required to serve in dual capacities,
shifting from quality verification of concrete mixing and
placing to other phases of the work as required. Quality
assurance representatives may also be required to verify
curing, protection, and cleanup. It is desirable to have
continuous quality verification of batching and mixing
operations.
(d) Ready-mix operations. When concrete is centrally
mixed at the plant, a quality assurance representative should
be on duty full time at the plant where he can observe and
test the mixed concrete and can reject concrete which fails
to meet job requirements. When concrete is transit-mixed,
full-time plant quality verification is desirable, but primary
responsibility for acceptance of concrete belongs to the
quality assurance representative at the site of the work. If
full-time plant quality verification is not possible, the plant
should be visited frequently to ensure that batching is
carried out properly.
(e) Small job. There is a tendency to overlook small
jobs and the small parts of large jobs. Frequently, small
structures such as curbs and sidewalks have very severe
exposure and require concrete of high durability. Although
a quality assurance representative on a small job may have
duties other than concrete quality verification, no concrete
placing should be started without a quality assurance
representative on hand.
(4) Records. The value of clear, concise, and
complete records is sometimes overlooked during the con-
struction of a project. In devising a system of reports, and
preparing forms for these reports, it should be realized that
these reports will constitute a part of the official record of
the construction operations and may be the sole source of
reliable information on the procedure, practices, and results
obtained during construction. Reports in various forms
should be made daily and at other stated intervals for
several purposes. Standard forms are available for reporting
most test results. Where necessary, special forms may be
devised on the project to suit project requirements. Reports
will supply information on, and preserve as a permanent
record, facts concerning progress of the work, factors
affecting progress, instructions given to contractors, samples
secured, tests made, and any other necessary data. Unusual
occurrences in the plant may be noted on the recorder chart
by the quality assurance representative or plant operator.
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82. EM 1110-2-2000
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The information should ultimately appear in a report. The
reports made by placing quality assurance representatives
and quality assurance representatives engaged on cleanup,
curing, finishing, and protection should follow a well-
devised standard form on which the essential facts are
recorded for the period of quality verification. Government
test results should include control charts and variability of
the material tested. Each such report form should also
provide space for recording unusual happenings and for any
pertinent remarks concerning shift operations.
9-2. Required Sampling and Testing for CQC and
GQA
The following tests are normally required for a major civil
works concrete construction project for CQC and GQA
purposes. The procedures and frequencies of all the
necessary CQC tests should be included in the contract
specification. Tests for GQA are at the Government’s
discretion and should not be specified in the specification
except those cases where sampling and facility are the
Contractor’s responsibility. The required frequencies for
GQA and government acceptance tests should be included
in the Engineering Considerations and Instructions to Field
Personnel for each project. The recommended testing
frequencies for GQA are listed in the following paragraphs.
a. Aggregate grading. In order to determine
compliance with the specification requirement that
aggregates must be within certain grading limits as delivered
to the mixers, samples must be obtained as delivered to the
mixer. On mass concrete projects containing 150-mm
(6-in.) NMSA, the specifications require that an automatic
small screening plant be included in the batch plant. On
concrete projects containing 75-mm (3-in.) NMSA, a cost
analysis should be made before specifying the automatic
screening plant. The automatic screening plant makes use
of angled quarry screens, which by their nature are 80-
percent efficient at the best and cannot be compared directly
to Gilson screens, which are 95- to 98-percent efficient.
The automatic screening plant must contain controls to vary
the angle and frequency (vibrations per minute) of each
individual screen. Optimum loading, screen angle, and
frequency of each screen must be established by the
Contractor before construction begins. Correlation tests with
Gilson sieving equipment must be performed before
construction and every 60 days while concrete production
continues. The quarry screens on the automatic screening
plant will normally require a larger screen than the Gilson
screens for comparable results. With such a device, the
sampling, screening, determination of mass, and disposal is
accomplished automatically. Normally, it is not necessary
to procure samples at any other location. Samples may be
procured at any point in the production line where it is
deemed necessary. Where 150-mm (6-in.) NMSA is used,
it might not be feasible to sample the 75- to 150-mm (3- to
6-in.) fraction from the weigh batcher. Then samples may
be obtained from the conveyor belt or other convenient
place as close as possible to the end of the handling
operations. When sampled from a conveyor belt, the belt
should be stopped, and the sample should consist of a
complete section and not hand-picked from the top. Where
aggregates are supplied by a commercial producer located
some distance from the project, sampling for acceptance
tests will not be made at the producer’s plant. Such tests
would not reflect the possible effects of segregation in
stockpiling at the project and breakage in handling.
(1) Frequency.
(a) On-site plant. During each 8-hr shift when
concrete is being produced, at least one sample of each size
of aggregate should be taken. During the early stage of a
large project, several samples per shift should be tested until
the production control has achieved uniformity. After 1
month, if the Contractor’s control testing has proven to be
satisfactory, frequency of government sampling may be
reduced to one-third of that stated above.
(b) Off-site commercial plant. The frequency of QA
testing of the aggregate grading at an offsite commercial
plant will vary somewhat with the quantity of concrete and
the rate of concrete usage from that plant where concrete is
supplied to many customers and the concrete mixture is
furnished by the contractor. For minor concrete jobs, the
aggregate should be tested before concrete placing begins
and once per week while concrete is being placed. On
larger structural concrete jobs, the aggregate grading should
be tested by the GQA representative before start of concrete
placement and at least twice per week thereafter while
concrete is being placed.
(2) Size of samples. Sample sizes for sieve analysis
are given in ASTM C 136 (CRD-C 103). For fine aggre-
gates and finer sizes of coarse aggregate, samples obtained
in accordance with CRD-C 100 may be reduced in size by
a sample splitter or by carefully following instructions for
quartering given in ASTM C 702 (CRD-C 118). For
aggregate sizes smaller than 37.5 mm (1-1/2 in.), the
required sample sizes are sufficiently large in relation to
individual particle size so that compliance with the grading
specification may be fairly determined by a single test. For
37.5 mm (1-1/2-in.) and larger sizes, however, this is not
true. While sample sizes given in ASTM C 136 (CRD-C
103) for nominal maximum aggregate sizes larger than
37.5 mm (1-1/2 in.) are practical for laboratory sieve
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83. EM 1110-2-2000
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analysis testing equipment, the samples are subject to large
random sampling errors. Therefore, compliance with speci-
fication should be determined from the average of five
consecutive tests. Whenever a single test result shows a
major deviation from specification requirements, the
frequency of sampling and testing should be accelerated to
as great an extent as practical until it is established whether
the indicated noncompliance was the result of sampling
error or the result of an actual deficiency in the aggregate
processing equipment. Sometimes a single retest will be
sufficient to establish the cause of the noncompliance. If
sampling and testing equipment is installed that is capable
of handling specimens five times as large as those required
by ASTM C 136, averaging of test results is not necessary.
b. Aggregate quality - large project. Paragraph 7-1
requires initial testing of the Contractor’s chosen aggregate
sources to confirm that the aggregate quality has not
changed since it was tested in the design stage and to
confirm that it meets aggregate quality specification
requirements. Quality testing by the Government should be
performed during the life of the contract at about 10 percent
of the rate listed in the CQC requirements of the
specifications. Tests performed by the Contractor under
CQC should be monitored carefully by the GQA
representative. Experience has shown that quality of
aggregate can change, either gradually, or at times
dramatically as production proceeds laterally and vertically
in the source. Failing quality tests will require additional
testing by the Contractor and by the Government. Resident
office personnel should record and monitor the location in
the quarry or pit from which the aggregate is being
produced. A change in visual appearance or quality test
results could signal a change in production location at the
source.
c. Free moisture on aggregates. Adjustments of
batch weights to compensate for variation in aggregate
moisture is a basic contractor responsibility. The
Contractor’s methods for complying with this requirement
should be reviewed and verified at least once weekly.
Whenever the concrete is considered out of control due to
slump or air content, the government testing should increase
in a cooperative effort with the Contractor in obtaining
testing information needed to perform the necessary
adjustments. When a moisture meter is required by the
specifications, its accuracy should be verified at least once
per week.
d. Slump and air content. The slump test ASTM C
143 (CRD-C 5) is made as a check on the uniformity of the
concrete and to determine whether the concrete being sent
to the forms is placable. Samples for slump and air content
tests may be taken and tested at the batch plant for onsite
plants; however, the required slump and air content is that
required at the placement. If slump or air content loss is
experienced, then occasional tests must be performed at the
placement site to determine amount of slump loss or air
content loss. In that case, slightly higher values may be
adopted for use at the plant, so that the proper slump and air
are obtained at the placement. Considerable slump loss and
air content loss are usually associated with conveying or
pumping concrete considerable distances. Correlation test
samples for compressive strength is also necessary when
considerable slump and air content loss is experienced.
Variation in slump is caused chiefly by variation in
aggregate moisture and air content. Whenever either or
both of these factors vary, slump tests should be made as
frequently as needed to ensure that the concrete is of the
required consistency. When the mixture is of the required
consistency, slump tests should be made at least twice per
shift for each concrete mixture being placed. Control of air
content is essential to the placeability and the durability of
concrete. When no control problems are encountered, the
air content should be determined at least twice per shift for
each concrete mixture being placed. When the concrete
contains a fly ash with a variable carbon content, the testing
rate should be increased. After 3 months, if the
Contractor’s control has been adequate, slump and air
content need to be measured by the Government only when
cylinders are fabricated.
e. Concrete temperature. The temperature of cooled
concrete should not be measured until 20 minutes after
mixing. If the largest aggregate was cooled for an
insufficient period of time, the particles may be only surface
cooled. If so, this fact will be reflected in the delayed
temperature reading. The sensing element of the
thermometer should be at least 3 in. below the surface of
the fresh concrete when the measurement is made. The
temperature of each concrete mixture should be checked
twice per shift when concrete is being placed.
f. Compressive strength.
(1) Purpose. Strength tests are performed for different
purposes depending on the type of construction and the
specification used. For mass-concrete structures where
mixture proportioning is provided by the Government,
strength tests are needed to measure the variability of the
concrete mixture. In this case, strength is not necessarily
the most critical factor concerning the concrete mixture.
Other considerations, such as durability or thermal cracking,
may dictate the w/c. Nevertheless, compressive strengths
are good indications of variations in other concrete
properties. For concrete structures where mixture
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proportioning is the Contractor’s responsibility, concrete
strength is a part of the acceptance requirements. The
strength criteria are normally determined by structural
requirement.
(2) Testing responsibility. The specifications should
require the Contractor to mold, protect, cure, and test
compressive strength cylinders on all concrete construction
where the Government furnishes the mixture proportions,
except for arch dam construction where the Government will
perform all the strength testing. The frequency of testing by
the Contractor should be in accordance with paragraph 9-
2f(4). In addition, the GQA representative should mold,
cure, protect, and test at least 1 set of test cylinders for each
10 sets of cylinders made by the Contractor. The GQA test
cylinders should be from the same batch of concrete as one
of the CQC test cylinders. After a minimum of 30 sets of
cylinders are tested, the resident engineer may choose to
lower the amount of government-molded, -cured, and -tested
cylinders to 5 percent (1 in 20) of the cylinders tested by
the Contractor if the CQC tests are proven satisfactory. A
10-percent differential in the test results between CQC tests
and GQA tests would be cause for further investigation of
the Contractor’s casting, curing, and testing procedures and
equipment.
(3) Sampling plan. The frequency of sampling,
number of cylinders made, and ages at which the cylinders
are tested will vary with the type and size of the project. At
the beginning of each project, a sampling plan will be
developed by the Government that is consistent with the
project specifications. The sampling plan should obtain
information on the quality of each class of concrete at the
least cost. The sampling plan must reflect the variability
characteristics of heterogeneous concrete. The individual
samples must be taken in such a manner that each sample
is selected in an unbiased manner. The number of test
specimens fabricated will depend on the number of ages at
which they are to be tested. For part of the work, two
specimens should be tested at the same age to derive the
within-batch coefficient of variation. A test is defined as
the average strength of all specimens of the same age,
fabricated from a sample taken from a single batch of
concrete. Samples should be obtained by means of a
random sampling plan designed to minimize the possibility
that choice will be exercised by the sampler. Probability
sampling of materials is discussed in ASTM E 105 (CRD-C
579). This procedure should be used for guidance in
developing a random sampling method. The sampling plan
should also include the predetermined sampling location
where representative samples will be obtained.
(4) Frequency and testing age. During the early stages
of a project, it is desirable to increase the frequency of
testing until control is established. Structural concrete
should normally be sampled once per shift and mass
concrete once per day for each concrete mixture placed.
When mixture proportions are provided by a division
laboratory, as would be the case of a large mass structure
such as a lock or dam, accelerated strength testing should be
used to control batching and mixing based on relationships
developed by the laboratory. Two specimens will normally
be molded and cured in accordance with ASTM C 684
(CRD-C 97), Method A. Where conditions are not suited to
this method, Method B or C may be used. Laboratory
mixture proportioning studies should be developed with the
same method that will be used on the project. The design
age should be decided by the designer depending on the
type of structure involved, the types of cementitious
materials and the loading conditions anticipated. As
examples, the design age for a large lock or dam may be
180 days or even 1 year if design loadings are not likely to
occur sooner. However, the design age for a bridge or
pumping station will likely be 28 days and could possibly
be shorter depending on the construction techniques used
and the construction and in-service loadings anticipated.
The information age could be selected to coincide with
form-stripping schedules, removal of shoring, or in the
absence of construction considerations at intervals such as
7, 14, or 28 days. In addition to control or acceptance
cylinders, occasionally there will be a need for extra
cylinders. With prestressed concrete, for example, when
prestressing is to be applied when the concrete attains its
loading strength, it will be necessary to test cylinders at
various ages. Sometimes field-cured cylinders are used in
determination of form removal time. A sampling plan guide
for number and test age of cylinders is shown in Table 9-1.
(5) Sampling and testing methods. On all projects,
concrete will be sampled in accordance with ASTM C 172
(CRD-C 4). The test specimens will be molded and cured
in accordance with ASTM C 31 (CRD-C 11). When the
nominal maximum size aggregate is larger than 50 mm
(2 in.), the concrete sample shall be wet sieved in
accordance with ASTM C 172 over a sieve having 50-mm
(2-in.) square openings. Concrete test specimens will be
tested in accordance with ASTM C 39 (CRD-C 14).
(6) Analysis of tests. Strength variation is the key
consideration in analysis of data derived from tests of
concrete cylinders. Because of this variation, statistical
methods are used to analyze and present the numerical data.
The magnitude of variations in the strength of concrete test
specimens depends on how well the materials, concrete
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85. EM 1110-2-2000
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Table 9-1
Number of Cylinders to Be Cast
Number of Test Specimens at Various Ages
Concrete Type 1 Day Information Age(s) Design Age
Structural & minor 1 2
Mass 2 1 2
manufacture, and testing are controlled. The strength results
will vary above and below an average and fall into some
probability distribution. The strength test results should be
evaluated to determine the within-batch-coefficient of
variation and overall standard deviation. ACI 214
provides details on these methods of analysis. The
procedures involve mathematical computations which lend
themselves to computer processing. There are many
commercial programs available for this purpose. The
selection of appropriate computer programs for evaluating
test data may be made with the advice of CECW-EG. The
standards for control are shown in Table 9-2 for 28-day
strength results. The standards for accelerated strength test
results will be developed by the division laboratory based on
an analysis of 28-day strength results and the accelerated
strength test results. After the first 30 test results are
available on the project, they should be analyzed for average
strength and standard deviation and the mixture proportions
adjusted as appropriate.
(a) Within-test coefficient of variation. Within-test
coefficient of variation is caused by fabricating, curing, and
testing the cylinders. When the coefficient of variation is
greater than 5.0 percent, the following procedures should be
evaluated:
• Sampling procedures
• Fabrication techniques
• Handling and curing cylinders
• Quality of molds
• Variation in curing temperatures
• Variation in curing moisture
• Delays in transporting to the laboratory
• Size of the test specimens
• Capping procedures
(b) Overall standard deviation. Overall standard
deviation is a term representing a value related to both
within-test variation and batch-to-batch variation. The
overall standard deviation is defined as the square root of
the sum of squares of within-test and batch-to-batch
standard deviations. The variation may be introduced by
practices in proportioning, batching, mixing, and
transporting concrete. When overall standard deviation is
higher than 600 psi, the following procedures should be
evaluated:
• Characteristics and properties of the ingredients
• Batching and mixing procedures
• Sampling procedures
• Causes for variation in w/c, such as aggregate
moisture
• Causes for variation in water requirements
(7) Control criteria. On projects where mixture
proportions were developed by the Contractor, the
Contractor shall submit revised proportions when the
compressive strength tests do not meet the specified criteria.
On projects where mixture proportions were developed by
a division laboratory, the area/resident engineer in concert
with engineering division personnel should revise the
proportions as necessary to meet the required average
strength criteria. In both cases, adjustments to the
procedures should be made after the first set of 30 tests if
the overall standard deviation is approaching or beyond the
limit of 600 psi.
(8) Prediction of later age strengths. Where possible,
the division laboratory will develop an appropriate
correlation of the relationship between accelerated tests and
standard cured compression tests. At the start of concrete
placement, testing should be performed at accelerated ages
and later age. After the first 30 tests, the linear regression
equation should be verified or reestablished. If there is a
discrepancy between equations, the division laboratory
should be consulted to analyze the data. As confidence is
gained with predicting later age strength with the linear
regression equation, the amount of later age testing may be
reduced by as much as 50 percent.
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Table 9-2
Standards of Control for Concrete Compressive Strength
Standards for Concrete Control
Class of
Operation
Excellent Very Good Good Fair Poor
Within test,
coefficient of
variation, percent
0 - 3.0 3.0 - 4.0 4.0 - 5.0 5.0 - 6.0 Above 6.0
Overall standard
deviation, psi
0 - 400 400 - 500 500 - 600 600 - 700 Above 700
9-3. Nondestructive Testing
a. General. Nondestructive testing of concrete as
described herein includes methods of tests on concrete
structures or structural members which do not reduce the
functional capability of the structure, although some of the
methods listed do require minor repairs if the concrete will
be exposed to view. The tests described are those which are
used to gain an indication of the quality of hardened
concrete in place.
b. Policy. Nondestructive testing will not be used in
lieu of compressive strength tests of cylinders, air content
tests by the pressure method, slump tests, or any other test
for the evaluation and acceptance of concrete placed on any
civil works projects.
c. Applicability. Nondestructive tests may be used to
locate areas of unsound concrete or concrete suspected of
being significantly below the specified levels of strength
required by the design or the required levels of durability.
If areas are located where unsound, weak, or deteriorated
concrete is likely, the condition of the concrete may be
confirmed by coring unless the structure is so heavily
reinforced that useful specimens cannot be obtained.
Nondestructive testing may also be used to indicate changes
with time in characteristics of concrete such as those caused
by the hydration of cement so that it provides useful
information in determining when forms and shoring may be
removed.
d. Nondestructive testing methods. The methods
discussed do not represent all the available methods but only
those that have been standardized by ASTM. More detailed
discussion of the advantages and limitations of these test
methods is given in ACI 228.1R.
(1) Rebound hammer (ASTM C 805 (CRD-C 22)).
The rebound hammer consists of a spring-loaded steel
hammer which, when released, strikes a steel plunger in
contact with the concrete surface, and rebounding indicates
a rebound number on a calibrated scale. Only the concrete
in the immediate vicinity of the plunger influences the
rebound number; therefore, the test is sensitive to the local
conditions where the test is performed. Because the
rebound hammer tests only the near-surface layer of
concrete, the rebound number may not be representative of
the interior concrete. The probable accuracy in predicting
concrete strength in a structure by this method is only
± 25 percent, so its use is clearly limited to attempting the
differentiation between areas of large quality variation in the
same structure. Closer accuracy can be obtained by
calibrating the hammer with project concrete of known
strength. The main advantage of the rebound hammer is its
extreme portability so that many tests may be made easily
in a short period of time.
(2) Penetration resistance (ASTM C 803 (CRD-C 59)).
The penetration-resistance test uses a powder-driven stud to
measure the penetration resistance of concrete. This test,
like the rebound hammer, is a hardness tester; however,
attempts continue to be made to correlate the penetration of
the stud to concrete strength. The apparatus is easily
portable, using a modified powder cartridge stud gun and
studs or probes. The resulting damage to the concrete
surface is minor and may be easily repaired. A large
number of tests may be completed in a relatively short
period of time. Attempts to correlate the penetration-
resistance test results with core tests and cylinder tests
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87. EM 1110-2-2000
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indicate coefficients of variation and range about 10 times
as large as the core and cylinder test results. Therefore, the
use of the this test should be limited to applications where
large variations are suspected in the concrete quality or to
determine the locations for borings.
(3) Cast-in-place pullout tests (ASTM C 900 (CRD-C
78)). Pullout tests use a hollow stem ram to pull a bolt with
a washer on its lower end that has been cast in the concrete
at the time of placement. The pullout assemblies are
incorporated into the formwork for critical structural
members. As an alternative, pullout assemblies may be cast
into large blocks which are cast at the same time as the
structural member and consolidated and cured in a similar
way. The main advantage of the pullout tests is that it does
produce a well-defined failure in the concrete and measures
a static strength property of the concrete in a structure. The
equipment is easily portable. The pullout strength does
correlate with compressive strength; however, the coefficient
of variation of pullout test results has been found to be
approximately 7 to 10 percent. This is about two to three
times greater than that of standard compressive strength
tests. The main limitations are that the test locations are
fixed at the time of placement which limits the usefulness
of the pullout test in troubleshooting problems suspected
after placement is completed and the necessity of repairing
the surface which is marred by a crater about 6 in. across.
Commercial inserts have embedment depths on the order of
1 to 2 in. Since the vibrator operator may notice where the
inserts are, the consolidation of concrete around them may
not be representative of the entire member.
(4) Maturity method (ASTM C 1074 (CRD-C 70)).
Assuming sufficient moisture is present, the rate of
hydration of the cementitious materials in a concrete mixture
is influenced by the concrete temperature. Therefore, the
strength of concrete at any age is a function of its thermal
history. The maturity method accounts for the combined
effects of temperature and time on strength development.
The concrete thermal history and a maturity function are
used to calculate a maturity value which quantifies the
combined effects of time and temperature. Concrete
strength is expressed as a function of its maturity by means
of a strength-maturity relationship. So, if samples of the
same concrete are subjected to different curing temperatures,
the strength-maturity relationship for that concrete and the
thermal histories of the samples can be used to estimate
their strengths. The strength-maturity relationship must be
established for the concrete to be used in the structure in
order to use the maturity method. ASTM C 1074 describes
the procedure to be followed in developing this relationship
using the concrete of interest. The temperature of history of
the in-place concrete is continuously monitored, and from
these data the in-place maturity is calculated. The in-place
concrete strength can then be estimated at any point in time
based upon the concrete maturity at that same time and the
strength-maturity relationship. Commercial instruments are
available which automatically compute concrete maturity;
however, care should be exercised in their use since the
maturity function used by the instrument may not be
applicable to the concrete in the structure. To use the
maturity method to estimate in-place concrete strength, there
must be sufficient moisture for continued hydration, and the
concrete in the structure must be the same as that used to
develop the strength-maturity relationship. Proper curing
assures the first condition will be met, and conducting
slump, air content, unit weight, and accelerated strength tests
on concrete representative of that going into the structure
will assure the latter condition is met. The maturity method
has obvious applications in the control of form stripping,
shoring removal, and termination of cold-weather protection.
(5) Cores (ASTM C 42) (CRD-C 27). Coring is
usually the method ultimately chosen to determine the in-
place characteristics of concrete especially if the dispute
involves payment to the Contractor or other problems such
as the location of the member or the amount of
reinforcement present. Planning for the core sampling and
laying out the drill holes should follow (ASTM C 823
(CRD-C 26)). In heavily reinforced structures, it may be
impossible to obtain a core sample from which compressive
strength specimens may be taken since reinforcing steel may
be so prevalent in the concrete that cores free of reinforcing
steel and having height-to-diameter ratios equal to 1 or more
cannot be obtained. It may be possible, however, to obtain
specimens from such cores which will allow a determination
of air-void system parameters (ASTM C 457 (CRD-C 42))
or analysis for the products of reactivity. Additionally, the
effect of severing reinforcing steel on the integrity of the
structure should be analyzed. If possible, the size of the
core taken should be related to the nominal maximum size
aggregate in the structure. If 37.5-mm (1-1/2-in.) maximum
size aggregate is used in the structure then 6-in. cores
should be drilled. In structures using larger aggregate, it
may be practical to take cores up to 18 in. in diameter, but
costs increase rapidly and the large core usually cannot be
taken to a depth of more than 3 or 4 ft. Coring may prove
expensive and the holes have to be backfilled, but the
resulting data are usually accepted as the best evidence of
the condition of the concrete in place.
(6) Pulse velocity method (ASTM C 597 (CRD-C
51)). This method involves the application of a mechanical
impulse to a solid mass of material. The speed of the
waves which are subsequently generated and which pass
through the material are dependent on the elastic properties
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88. EM 1110-2-2000
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of the material. The pulses can be generated either by a
hammer blow or by an electroacoustic transducer. The
pulse velocity method may be used to determine the
uniformity of concrete. However, a number of factors affect
pulse velocity measurements, including concrete moisture
content and the presence of reinforcing steel. Reinforcing
steel may be especially troublesome if it is oriented parallel
to the pulse-propagation direction. The resulting apparent
velocity through such a member will be greater than the
actual velocity through the concrete. Failure to account for
the presence and orientation of reinforcing steel may lead to
inaccurate conclusions regarding the concrete quality. While
pulse-velocity equipment is commercially available, its use
and the interpretation of the pulse-velocity measurements
requires special training and techniques.
(7) Other methods. Other methods in addition to
those above are in the development stages. Contact WES
for additional information.
9-4. Preplacement Quality Verification
The quality of all concrete placement areas should be
verified prior to the actual placement of any concrete. For
complicated placements, these quality verifications should be
made as each element of the preparation for actual
placement is completed. That is, foundation preparation,
joint preparation, form installation, the placement of
reinforcing bars, all embedded metal work, waterstops,
conduits, mechanical piping, and cleanup should be verified
for quality and checked out as each is completed. Other
items that must be kept in mind at all times during all
phases of this work are the provisions for safety and access
to the placements, including all scaffolding, walkways, work
platforms, ladders, and railings along with whatever weather
protection and drainage provisions are required. If each
element of this preparation is thoroughly verified as it is
completed, it will then only require a cursory verification
immediately prior to the concrete placement to be assured
that the conditions have not changed. On a small or simple
placement, the final quality verification may be all that is
required prior to concrete placement. These preplacement
verifications will be more systematic and accurate if a
checklist is used. This checklist is to be initiated and dated
by the representatives of the Contractor and the Government
as each element in this preparation is completed. These
checklists are known by various names, such as lift
checkout cards and form checkout cards. The format of
these checklists can vary according to the project
requirements and the practice of the individual districts. All
essential information is recorded. A separate form or
checkout card is to be prepared for each concrete placement
and retained in the Government’s official project files. The
Guide Specifications "Mass Concrete" (CW-03305) and
"Cast-In-Place Structural Concrete" (CW-03301) also require
the Contractor to provide a written report certifying that all
elements of the placement are ready to receive concrete.
While it has become the practice in some districts and
divisions for the Contractor’s representative and the Corps’
quality assurance representative to jointly verify and sign the
checkout card, it should be kept in mind that this is, in fact,
the sole responsibility of the contractor and not be inferred
as a joint responsibility. The advantage of a jointly signed
card is that it establishes the means by which both the
Corps’ quality assurance representative and the contractor’s
quality control representative will be satisfied that the
elements of the placement meet the project specification
requirements before the concrete placement begins. Figure
7-1 is an example of a form checkout record.
9-5. Project Laboratory
a. General. A government field laboratory should be
provided as close as possible to the mixing plant. The
building housing the laboratory normally includes office
space for the concrete personnel and facilities for filing the
project concrete records.
b. Space requirements.
(1) Large-volume mass concrete project. At least
1,000 ft2
of work space, exclusive of office space, should be
provided for major mass concrete projects where it is
expected that concrete will be placed on a continuous day-
to-day basis throughout the construction season.
(2) Other. At least 500 ft2
of work space, exclusive
of office space, should be provided for moderate size
projects.
c. Equipment.
(1) Large-volume mass concrete project. Storage
tanks with a capacity of 300 cylinders and a 200,000-lbf
compression testing machine, complying with requirements
of ASTM C 39 (CRD-C 14), should be provided. New
machines being purchased and older machines, returned to
the manufacturer for repair, should be required to comply
with the 1-percent accuracy requirement. Older machines,
which are not under manufacturer’s warranty and are
presently in use, should be required to comply with a ± 3-
percent accuracy requirement. Aggregate testing equipment
should include that equipment necessary to perform tests for
absorption, density, surface moisture, and sieve analysis.
Heavy-duty laboratory screening equipment, such as the
Gilson for coarse aggregate and the Ro-Tap for fine
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aggregate, should be provided. Concrete testing equipment
includes that equipment necessary for determining air
content and slump and for molding test specimens. The
laboratory should not include a concrete mixer.
(2) Other. Moderate size projects should include a
curing tank with a capacity of 100 cylinders. If a
compression testing machine is not available, cylinders may
be shipped to either a division laboratory or large-volume
project for testing. Aggregate and concrete testing
equipment should be the same as for a large project. The
laboratory facilities for a small project should be limited to
equipment for measuring air content and slump and for
molding test specimens. Curing of test cylinders and
transportation to the laboratory for testing must be in strict
accordance with ASTM C 31 (CRD-C 11).
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Chapter 10
Special Concretes
10-1. General
For purposes of this manual, special concretes are
considered to be those which contain materials that are not
routinely used in conventional structural or mass concrete,
those which are not proportioned using procedures given in
CRD-C 99, or those which are placed with equipment or by
methods which require additional attention be given by the
Contracting Officer to assure the required quality is
achieved. Those special concretes for which detailed
guidance is given in other Corps publications are not
discussed in this chapter.
10-2. Preplaced-Aggregate Concrete
a. General. Preplaced-aggregate (PA) concrete is
produced by placing coarse aggregate in a form and later
injecting a portland-cement-sand fly ash grout, usually with
chemical admixtures, to fill the voids. The smaller-size
coarse aggregate is not used in the mixture to facilitate grout
injection. It is primarily applicable to the repair of existing
concrete structures. PA concrete may be particularly
suitable for underwater construction, placement in areas with
closely spaced reinforcing steel and cavities where overhead
contact is necessary, and in areas where low volume change
is required. It differs from conventional concrete in that it
contains a higher percentage of coarse aggregate since the
coarse aggregate is placed directly into the forms with point-
to-point contact rather than being contained in a flowable
plastic mixture. Therefore, hardened PA concrete properties
are more dependent on the coarse aggregate properties.
Drying shrinkage of PA concrete may be less than one-half
that of conventional concrete, which partially accounts for
the excellent bond between PA concrete and existing
roughened concrete. The compressive strength of PA
concrete is dependent on the quality, proportioning, and
handling of materials but is generally comparable to that
achieved with conventional concrete. The frost resistance of
PA concrete is also comparable to conventional air-entrained
concrete assuming the grout mixture has an air content, as
determined by ASTM C 231 (CRD-C 41) of approximately
9 percent. PA concrete may be particularly applicable to
underwater repair of old structures and underwater new
construction where dewatering may be difficult, expensive,
or impractical. Bridge piers and abutments are typical of
applications for underwater PA concrete construction or
repair. A detailed discussion of PA concrete is provided in
ACI 304.R.
b. Applications. PA concrete has been used on
different types of civil works construction including:
(1) Resurfacing of lock chamber walls.
(2) Underwater repair to lock guide walls.
(3) Resurfacing of spillways.
(4) Construction of plugs to close temporary sluices
through a dam.
(5) Filling of temporary fish ladders through a dam.
(6) Scroll case embedment.
c. Materials and proportioning. Intrusion grout
mixtures should be proportioned in accordance with
ASTM C 938 (CRD-C 615) to obtain the specified
consistency, air content, and compressive strength. The
grout mixture should also be proportioned such that the
maximum w/c complies with those given in Table 4-1.
Compressive strength specimens should be made in
accordance with ASTM C 943 (CRD-C 84). Compressive
strength testing of the grout alone should not be done to
estimate the PA concrete strength because it does not reveal
the weakening effect of bleeding. However, such testing
may provide useful information on the potential suitability
of grout mixtures. The ratio of cementitious material to fine
aggregate will usually range from about 1 for structural PA
concrete to 0.67 for mass PA concrete. A grout fluidifier
meeting the requirements of ASTM C 937 (CRD-C 619) is
commonly used in the intrusion grout mixtures to offset
bleeding, to reduce the w/c and still provide a given
consistency, and to retard stiffening so that handling times
can be extended. Grout fluidifiers typically contain a water-
reducing admixture, a suspending agent, aluminum powder,
and a chemical buffer to assure timed reaction of the
aluminum powder with the alkalies in the portland cement.
Products proposed for use as fluidifiers which have no
record of successful prior use in PA concrete may be
accepted contingent on successful field use. ASTM C 937
requires that intrusion grout made as prescribed for
acceptance testing of fluidifiers have an expansion within
certain specified limits which may be dependent on the
alkali content of the cement used in the test. Experience
has shown, however, that because of the difference in
mixing time and other factors, expansion of the field-mixed
grout ordinarily will range from 3 to 5 percent. If, under
field conditions, expansion of less than 2 percent or more
than 6 percent occurs, adjustments to the fluidifier should be
made to bring the expansion within these limits. The
fluidifier should be tested under field conditions with job
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materials and equipment as soon as practicable so that
sufficient time is available to make adjustments in the
fluidifier if necessary. If the aggregates are potentially
alkali reactive, the total alkali content of the portland cement
plus fluidifier added to increase expansion should not
exceed 0.60 percent, calculated as equivalent sodium oxide
by mass of cement. The grout submitted for use may
exhibit excess bleeding if its cementitious material to fine
aggregate ratio is different than that of the grout mixture
used to evaluate the fluidifier. Expansion of the grout
mixture should exceed bleeding at the expected in-place
temperatures. Grout should be placed in an environment
where the temperature will rise above 40 °F, since
expansion caused by the fluidifier ceases at temperatures
below 40 °F. This condition is normally readily obtainable
when PA concrete is placed in massive sections or
placements are enclosed by timber forms. If an air-
entraining admixture is used in the PA concrete, adjustments
in the grout mixture proportions may be necessary to
compensate for a significant strength reduction caused by
the combined effects of entrained air and the hydrogen
generated by the aluminum powder in the fluidifier.
However, these adjustments must not reduce the air content
of the mixture to a level that compromises its frost
resistance. The largest practical NMSA should be used to
increase the economy of the PA concrete. A 37.5-mm (1-
1/2-in.) NMSA will typically be used in much of the PA
concrete; however, provisions are made for the use of
75-mm (3-in.) NMSA when it is considered appropriate. It
is not expected that many situations will arise where the use
of aggregate larger than 50 mm (2 in.) will be practical.
Pozzolan is usually specified to increase flowability of the
grout.
d. Preplacing aggregate. Care is necessary in
preplacing the coarse aggregate if excessive breakage and
objectionable segregation are to be avoided. The difficulties
are magnified as the nominal maximum size of the
aggregate increases, particularly when two or more sizes are
blended. Therefore, the Contractor’s proposed methods of
placing aggregate should be carefully reviewed to ensure
that satisfactory results will be obtained. Coarse aggregate
must be washed, screened, and saturated immediately prior
to placement to remove dust and dirt, and to eliminate
coatings and undersize particles. Washing in forms should
never be permitted because fines may accumulate at the
bottom.
e. Contaminated water. Contaminated water is a
matter of concern when PA concrete is placed underwater.
Contaminants present in the water may coat the aggregate
and adversely affect the setting of the cement or the bonding
of the mortar to the coarse aggregate. If contaminants in
the water are suspected, the water should be tested before
construction is permitted. If contaminants are present in
such quantity or of such character that the harmful effects
cannot be eliminated or controlled, or if the construction
schedule imposes a long delay between aggregate placement
and grout injection, PA concrete should not be used.
f. Preparation of underwater foundations. Difficulty
has been experienced in the past with cleanup of
foundations in underwater construction when the foundation
material was glacial till or similar material. The difficulty
develops when as a result of prior operations, an appreciable
quantity of loose, fine material is left on the foundation or
in heavy suspension just above the foundation. The fine
material is displaced upward into the aggregate as it is being
placed. The dispersed fine material coats the aggregate or
settles and becomes concentrated in the void spaces in the
aggregate just above the foundation thus precluding proper
intrusion and bond. Care must, therefore, be exercised to
ensure that all loose, fine material is removed insofar as
possible before placement of aggregate is allowed to
commence.
g. Pumping. Pumping of grout should be continuous
insofar as practical; however, minor stoppages are
permissible and ordinarily will not present any difficulties
when proper precautions are taken to avoid plugging of
grout lines. The rate of pumping should be regulated by use
of sounding wells so that the preplaced aggregate is slowly
intruded to allow complete and uniform filling of all voids.
The rate of grout rise within the aggregate should be
controlled to eliminate cascading of grout and to avoid form
pressures greater than those for which the forms were
designed. For a particular application, the grout injection
rate will depend on form configuration, aggregate grading,
and grout fluidity.
h. Joint construction. A cold joint is formed in PA
concrete when pumping is stopped for longer than the time
it takes for the grout to harden. When delays in grouting
occur, the insert pipes should be pulled just above the grout
surface before the grout stiffens, and then rodded clear.
When pumping is ready to resume, the pipes should be
worked back to near contact with the hardened grout surface
and then pumping resumed slowly for a few minutes.
Construction joints are formed in a similar manner by
stopping grout rise approximately 12 in. below the aggregate
surface. Care must be taken to prevent dirt and debris from
collecting on the aggregate surface or filtering down to the
grout surface. If construction joints are made by bringing
the grout to the surface of the coarse aggregate, the joint
surfaces should be cleaned and prepared as discussed in
paragraph 7-6 d of this manual.
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i. Grouting procedure. The two patterns for grout
injection are the horizontal layer and the advancing slope.
Regardless of the system used, grouting should start from
the lowest point in the form.
(1) Horizontal layer. In this method grout is injected
through an insert pipe to raise the grout until it flows from
the next insert hole 3 to 4 ft above the point of injection.
Grout is then injected into the next horizontally adjacent
hole, 4 or 5 ft away, and the procedure is repeated
sequentially around the member until a layer of coarse
aggregate is grouted. Successive layers of aggregate are
grouted until all aggregate in the form has been grouted.
(2) Advancing slope. The horizontal layer method is
not practical for construction of such slabs when the
horizontal dimensions are large. In situations such as this,
it becomes necessary to use an advancing slope method of
injecting grout. In this method, intrusion is started at one
end of the form and pumping continued until the grout
emerges on the top of the aggregate for the full width of the
form and assumes a slope which is advanced and maintained
by pumping through successive rows of intrusion pipes until
the entire mass is grouted. In advancing the slope, the
pumping pattern is started first in the row of holes nearest
the toe of the slope and continued row by row up the slope
(opposite to the direction of advance of slope) to the last
row of pipes where grouting has not been completed. This
process is repeated, moving ahead one row of pipes at a
time as intrusion is completed.
(3) Grout insert pipes and sounding devices. The
number required and the location and arrangement of grout
insert pipes will depend on the size and shape of the work
being constructed. For most work, grout insert pipes will
consist of pipes arranged vertically and at various
inclinations to suit the configurations of the work. The
guide specification provides for the option of the diameter
of the grout insert pipes being either 3/4, 1, or 1-1/2 in.
Generally, either a diameter of 3/4 or 1 in. would be
allowed for structural concrete having a maximum size
aggregate of 37.5 mm (1-1/2 in.) or less. If the preplaced
aggregate has a maximum size larger than 37.5 mm
(1-1/2 in.), the grout insert pipes should be 1-1/2 in. in
diameter. Intrusion points should be spaced about 6 ft
apart; however, spacing wider than 6 ft may be permissible
under some circumstances, and spacings closer than 6 ft will
be necessary in some situations. Normally, one sounding
device should be provided for each four intrusion points;
however, fewer sounding devices may be permissible under
some circumstances. In any event, there should be enough
sounding devices, and they should be arranged so that the
level of the grout at all locations can be accurately
determined at all times during construction. Accurate
knowledge of the grout level is essential to:
(a) Check the rate of intrusion.
(b) Avoid getting the grout too close to the level of
the top of the aggregate when placement of the aggregate
and intrusion are progressing simultaneously.
(c) Avoid damage to the work which would occur if
a plugged intrusion line were washed out while the end of
the line was within the grout zone.
Sounding devices usually consist of wells (slotted pipes)
through which the level of the grout may be readily and
accurately determined. If sounding devices other than wells
are proposed, approval should be based on conclusive
demonstration that such devices will readily and accurately
indicate the level of the grout at all times. In repairing
vertical surfaces, such as lock chamber walls or sloping
surfaces which are substantial distances and are relatively
thin (up to about 2 ft thick), the grout is brought up
uniformly from the bottom. Intrusion points for such work
should be arranged in horizontal rows with the rows spaced
not more than 4 ft apart horizontally. Holes in adjacent
horizontal rows should be staggered so that a hole in any
row is at the midpoint of the space between holes in the
adjacent rows above and below. Intrusion is controlled by
pumping through all holes in each horizontal row until grout
flows from all holes in the row above. Grouting then
proceeds through the next row above after the holes below,
which have just been grouted are plugged. The process is
repeated until a section is completed. The bottom row of
holes should be placed at the bottom of the form.
j. Finishing unformed surfaces. If a screeded or
troweled finish is required, the grout should be brought up
to flood the aggregate surface and any diluted grout should
be removed. A thin layer of pea gravel or 3/8- to 1/2-inch
crushed stone should then be worked into the surface by
raking and tamping. After the surface has stiffened
sufficiently, it may be finished as required. A finished
surface may also be obtained on PA concrete by adding a
bonded layer of conventional concrete of the prescribed
thickness to the PA concrete surface. The PA concrete
surface should be cleaned and grouted prior to receiving the
topping.
10-3. Underwater Concrete
a. General. For underwater concrete placements to
be successful, careful planning and execution are essential.
The location and size of the area to be concreted should be
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well defined and thoroughly cleaned so that it is free of
mud, silt, and debris. The extent of the cleaning effort will
be determined largely by whether the concrete is being
placed into a new structure or being used to repair an
existing structure. All marine growth, sediment, debris, and
deteriorated concrete must be removed prior to placing new
concrete. Waterjets and self-propelled vehicles have been
effective in most cleaning applications. Airlifts should be
used to remove sediment and debris from depths of 25 to
75 ft. If the concrete is being used to repair an existing
structure, an appropriate number of anchors should be
grouted into the existing concrete to tie the new concrete to
the existing concrete. The concrete must be protected from
the water until it is in place so that the cement fines cannot
wash away from the aggregate. This protection can be
achieved through the proper use of placing equipment, such
as tremies and pumps. The velocity of the water
immediately adjacent to the placement should not exceed
5 ft/sec. The quality of the in-place concrete can be
enhanced by the addition of an AWA which increases the
cohesiveness of the concrete. Concrete mixtures to be
placed underwater must be highly workable and cohesive.
The degree of workability and cohesiveness can vary
somewhat depending upon the type of placing equipment
used and the physical dimensions of the area to be filled
with concrete. A dense, homogeneous mass of concrete
having hardened properties equivalent to those of concrete
placed in the dry should be the result of a good underwater
concrete operation.
b. Tremie concrete. A massive and confined
placement, such as a cofferdam or a bridge pier, could be
completed with a conventional tremie concrete mixture. The
desired workability can normally be produced by using 19.0-
or 37.5-mm (3/4- or 1-1/2-in.) NMSA and a w/c not
exceeding 0.45. An increase in fine aggregate content of
approximately 6 percent, as compared to a conventional
concrete mixture, may be necessary. Rounded aggregates
are preferred over crushed aggregates for both coarse and
fine sizes. Listed below is a typical mixture for a
conventional tremie mixture:
Portland cement 600 lb/cu yd
Fly ash 100 lb/cu yd
19.0-mm (3/4-in.) NMS natural gravel
Natural sand
Sand-aggregate ratio = 0.45
w/c = 0.45
WRA
Air content = 6 %
Slump = 6 to 8 in.
Mixtures of this type must be fully protected from exposure
to water until in place. Whether being placed by tremie or
pump, it is mandatory that the seal be maintained. Once
concreting is underway, the bottom of the pipe should be
kept buried in the concrete about 5 ft below the surface of
the concrete. AWA’s can be used in these mixtures but are
not necessary, although their use should enhance the fresh
properties of the concrete. Spacing of tremie pipes should
not exceed 15 ft. A more complete discussion of tremie
concreting practices is given in ACI 304R.
c. Pumped concrete for use underwater. Many repair
situations require that the concrete flow laterally in thin lifts
for a substantial distance. This exposes the concrete to
much water while being placed. For this type of placement,
an AWA should be used to enhance the cohesiveness of the
concrete. The cohesiveness and flowability required cannot
normally be obtained without use of an AWA. Water-
reducing or HRWRA’s are usually necessary as well. Trial
batches must be made to ensure compatibility between
AWA’s, WRA’s, and HRWR’As. The desired workability
can normally be produced with rounded aggregates of
19.0-mm (3/4-in.) NMS or smaller and a w/c not exceeding
0.45. An increase of approximately 6 percent in fine
aggregate content, as compared to a conventional concrete
mixture, may be necessary. When a repaired area will be
subjected to abrasion-erosion, silica fume should be
considered to enhance the hardened properties of the
concrete. Silica fume will also increase the cohesiveness of
the fresh concrete mixture. Listed below is a typical
mixture for proportioning an underwater concrete mixture
for use in repairing an existing structure:
Portland cement 600 lb/cu yd
Fly ash 30 lb/cu yd
Silica fume 40 lb/cu yd
19.0-mm (3/4-in.) NMS or smaller natural gravel
Natural sand
Sand-aggregate ratio = 0.45
w/c = 0.40
AWA
WRA or HRWRA
Air content = 6 %
Slump = 8 to 10 in.
Pumping is the preferred method of placement, although
tremies may be used on some repair jobs. Pumping
distances should be kept to a minimum. If the pumping
distance exceeds 250 ft, pumping pressures will likely
increase significantly due to the increased cohesiveness
imparted by the AWA. Excessive pumping pressures will
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94. EM 1110-2-2000
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necessitate relocating the pump, using staged pumps to
shorten the pumping distance, or modifying the concrete
mixture or reducing the amount of AWA’s. Some
adjustments may reduce the cohesiveness of the concrete,
making it more susceptible to washout. If the pumping
distance is 150 ft or less, the cohesiveness imparted by an
AWA actually improves the pumpability of concrete. When
AWA’s are used, it is not as critical to keep the discharge
end of the tremie or the pump line embedded in the concrete
as it is when they are not used. However, the concrete
should not be unnecessarily exposed to water during
placement. Once in place, concretes of this type can flow
up to 30 ft without harmful washout or segregation.
Pumped concrete is discussed in detail in paragraph 10-6 of
this manual. Additional information on pumped concrete for
use under water is given in WES Technical Report
REMR-CS-18 (Neeley 1988) and EM 1110-2-2002,
"Evaluation and Repair of Concrete Structures."
10-4. Blockout Concrete
a. General. The use of blockouts in concrete
members is often necessary to embed seats, guides, rails,
piping, and electrical and mechanical systems into concrete
placements. Prior to placement of blockout concrete, the
blockout or recess should be carefully inspected to assure all
surfaces are thoroughly cleaned of all loose material, oil,
grease, and other material which might reduce or destroy
bond between surfaces of the blockout or recess and the
new concrete. Care should also be exercised in assuring
that blockout concrete is properly consolidated, particularly
in those blockouts or recesses which are heavily congested
with a combination of embedments and reinforcing steel.
b. Blockout concrete proportions. Blockout concrete
is normally proportioned to meet the same strength criteria
as adjacent concrete. The NMSA is usually 19.0 mm
(3/4 in.). Bonding of the blockout concrete to the adjacent
formed concrete surfaces is most important. These surfaces
must be cleaned of any laitance and any oil, grease, or
foreign matter. Cleanup of these surfaces should be the
same as for any other surface to which concrete is to be
bonded, although sandblasting or high-pressure water jet
blasting is not usually necessary for block outs on vertical
surfaces. The fluidifying-expanding agent should be used in
such proportion that the paste portion of the blockout
concrete, when tested separately, will have an expansion of
2 to 4 percent when tested in accordance with ASTM C
940. An expansive admixture conforming to ASTM C 937
(CRD-C 619) should be specified for all vertical blockouts
and any other blockouts which are formed or otherwise
confined on all sides. Where the blockout is on a horizontal
surface and the top of the blockout concrete is to be hand
finished, the expansive admixture should not be used. An
epoxy bonding compound meeting ASTM C 881, Type V
(CRD-C 595), has been successfully used for bonding of
blockout concrete to adjacent concrete although timing can
be critical. The new concrete must be placed while the
epoxy is still tacky and before it hardens.
10-5. High-Strength Concrete
a. General. High-strength concrete has seen
increasing use in recent years as compressive strength
requirements have increased and new applications have been
developed. Early applications emphasized its use to reduce
column dimensions. It has now been used to meet special
project objectives such as in large composite columns,
stiffer structures, bridges, stilling basins, and structures
subject to chemical attack. The increased use of high-
strength concrete has, in turn, prompted the application of
more stringent quality control requirements. A thorough
discussion of high-strength concrete is given in ACI 363R.
b. Definition. The definition of high-strength concrete
is concrete having a 28-day design compressive strength
over 6,000 psi (41 MPa) (ACI 116R). In regions where
concretes having strengths up to 5,000 psi are readily
available, 9,000 psi might be considered to be high-strength
concrete. However, in regions where concrete having a
compressive strength of 9,000 psi is readily available,
12,000 psi might be considered to be high-strength concrete.
In many instances, the required compressive strength is
specified at 56- or 90-days age rather than 28-days age to
take better advantage of pozzolans in the concrete.
c. Materials. When high-strength concrete is to be
used, all materials must be carefully selected. Items to be
considered in selecting materials include cement
characteristics, aggregate size, strength, shape, and texture,
and the effects of chemical admixtures and pozzolans.
High-strength concretes are typically proportioned with high
cement contents, low w/c, normal weight aggregate,
chemical admixtures, and pozzolans. Trial mixtures are
essential to ensure that required concrete properties will be
obtained.
d. Cement type. The choice of portland cement is
very important. Type I cement is appropriate for use in
most high-strength concrete. If high initial strength is
required, such as in prestressed concrete, Type III cement
may be more appropriate. However, the high cement
contents associated with high-strength concretes will cause
a high temperature rise within the concrete. If the heat
evolution is expected to be a problem, a Type II moderate-
heat-of-hydration cement can be used, provided it meets the
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95. EM 1110-2-2000
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strength-producing requirements. However, even within a
given type of cement, such as Type I, II, or III, different
brands can have different strength development
characteristics because of the variations in their physical and
chemical compositions.
e. Cement content. Cement contents typically range
from 660 to 940 lb/yd3
. However, higher strengths do not
always accompany higher cement contents. The concrete
strength for any given cement content will vary with the
water demand of the mixture and the strength-producing
characteristics of the cement being used. The optimum
cement content will depend upon the combinations of all
materials being used and is best determined by trial batches.
f. Aggregates. The choice of aggregates is very
important to the ultimate strength that a high-strength
concrete will develop since they occupy the largest volume
of any of the constituents in the concrete. Most high-
strength concrete has been produced using normal weight
aggregates. Some high-strength lightweight aggregates and
heavyweight aggregates have also been used successfully in
high-strength concretes. In general, crushed coarse
aggregates, 19.0-mm (3/4-in.) nominal maximum size or
smaller, are preferred for high-strength concretes because
their shape and surface texture enable the cement paste to
bond to them better than rounded natural aggregates.
Smaller size aggregates have better bond strengths and less
severe stress concentrations around the particles. The ideal
aggregate should be clean, cubical, angular, 100-percent
crushed aggregate with a minimum of flat and elongated
particles. The volume of coarse aggregate can usually be
increased up to 4 percent from that recommended in
ACI 211.1 for conventional concretes. Natural fine
aggregates are preferred because they require less mixing
water and provide better workability. Since the concrete has
a high cement content, sands having a high fineness
modulus (about 3.0) usually give better workability and
strength. Sands having fineness moduli of 2.5 and below
usually increase the water demand and give the concrete a
sticky consistency, making it more difficult to place.
g. Pozzolans. Pozzolans in quantities ranging from 15
to 40 percent by mass of cement are frequently used to
supplement the portland cement in high-strength concrete.
Silica fume is generally used in amounts ranging from 5 to
10 percent by mass of cement. The volume increase in
cementitious materials resulting from the addition of a
pozzolan is usually offset largely by a decrease in the fine
aggregate content. Depending on the type of pozzolan used,
the water demand of the concrete mixture may be increased
or decreased. When silica fume is used, the water demand
will be increased and make the use of an HRWRA
necessary. See paragraph 10-10 of this manual for more
information on silica-fume concrete.
h. Use of HRWRA. HRWRA’s are frequently used in
high-strength concrete to lower the w/c. They can also be
used to increase the workability of the concrete. In some
cases, an HRWRA may be used in combination with a
conventional WRA or a retarding admixture to reduce slump
loss. Depending on the specified w/c, the required
workability, and the materials being used, a conventional
WRA used at a high dosage may provide the necessary
water reduction. Larger-than-normal dosages of air-
entraining admixtures are usually required to entrain air in
high-strength concretes due to the high cement contents.
i. Workability. Due to their cohesiveness, high-
strength concretes can be more difficult to place than
conventional concretes. The mixture should be easy to
vibrate and mobile enough to pass through closely spaced
reinforcement. A slump of about 4 in. will usually provide
the required workability. However, all structural details
should be considered prior to specifying the fresh properties
of the concrete mixtures. Also, the rapid slump loss
exhibited by many high-strength concretes should be
considered. Slumps of less than 3 in. have been difficult to
place without special equipment and procedures.
j. Proportioning. More laboratory trial batches may
be necessary to properly proportion a high-strength concrete
mixture than would be required to proportion a conventional
concrete mixture. Once a mixture has been proportioned in
the laboratory, field testing with production-size batches is
recommended. Frequently, the strength level that can be
reasonably achieved in the field will be lower than that
attained in the laboratory batches. The water demand may
also vary from that determined in the laboratory.
Production and quality control procedures can be evaluated
more effectively when production-size batches are produced
using the equipment and personnel that will be doing the
actual work.
k. Material handling. The control, handling, and
storage of materials need not be significantly different from
the procedures used for conventional concrete. However,
some emphasis on critical points is prudent. The
temperature of all ingredients should be kept as low as
possible prior to batching. It may be necessary to make
provisions to lower the initial temperature of the concrete by
using chilled water, ice, or liquid nitrogen. Delivery time
should be reduced to a minimum and special attention given
to scheduling and placing to avoid having trucks waiting to
unload. Where possible, the batching facilities should be
located at or near the job site to reduce haul time. Extended
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96. EM 1110-2-2000
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haul times can result in a significant increase in temperature
and loss of slump and should be avoided.
l. Preparation for placing. Preparation for placing
high-strength concrete should include recognition that
certain unusual conditions will exist before any placement
begins. Since the effective working time of the concrete is
expected to be reduced, preparation must be made to
transport, place, consolidate, and finish the concrete as
quickly as possible. Proper planning, skilled workmen,
adequate equipment, and stand-by equipment are all
essential to a successful high-strength concrete placement.
m. Curing. Proper curing is critical to the production
of high-strength concrete. The potential strength and
durability of any concrete, especially high-strength concrete,
will be fully developed only if it is properly cured for an
adequate period prior to being placed in service. Water
curing of high-strength concrete, especially at early ages, is
required because of the low w/c’s. If the w/c is below 0.40,
the degree of hydration will be significantly reduced if free
water is not provided during curing. Water curing will
allow maximum hydration of the cement.
n. Testing. Since much of the interest in high-strength
concrete is limited primarily to compressive strength, these
measurements are of primary concern in the testing of high-
strength concretes. Careful attention should be given to all
details of the test methods being used while fabricating,
curing, and testing compressive strength specimens.
Standard specimens are 6-in.-diameter by 12-in.-high
cylinders; however, 4-in.-diameter by 8-in.-high cylindrical
specimens have also been used to determine the compressive
strength of high-strength concretes. The 4-in.-diameter by
8-in.-high specimens usually exhibit somewhat higher
compressive strengths and more variability than the standard
size specimens. Even so, proper testing procedures and a
suitably accurate and stiff testing machine are more critical
to attaining good results than is the specimen size. High-
strength sulfur mortar may be used to cap specimens having
compressive strengths up to 10,000 psi. Specimens
expected to have compressive strengths above 10,000 psi
should have their ends formed or ground to the required
tolerance. A caution should be added that these higher-
strength concretes require a corresponding larger capacity
compression testing machine.
10-6. Pumped Concrete
a. General. Pumped concrete can be used for most
structural concrete construction but is most useful where
space for construction equipment is limited or access is
difficult. Concrete pumps can be either truck- or trailer-
mounted and range from small units, exerting pressures
from 250 to 300 psi and outputs of 15 to 30 yd3
/hr, to large
units, exerting pressures of 1,000 psi and outputs up to 150
yd3
. The effective capacity of a pump depends not only on
the pump itself but also on the complete system. Several
factors including line length, number of bends in the line,
type of line, size of line, height to which the concrete is
being pumped, and the concrete mixture affect the effective
working capacity of a concrete pump. An excellent
reference is ACI 304.2R.
b. Pump lines. Pump lines are usually a combination
of rigid pipe and heavy-duty flexible hose. Acceptable rigid
pipe can be made of steel or plastic and is available in sizes
from 3 to 8 in. in diameter. Aluminum alloy pipe should
not be used as pump line. Flexible hose is made of rubber,
spiral wound flexible metal, and plastics. It is useful in
curves, difficult placement areas, and as connections to
moving cranes but exhibits greater line resistance to the
movement of concrete than rigid pipe and may have a
tendency to kink. To obtain the least line resistance, the
pipeline should be made up primarily of rigid pipe with
flexible hose only where necessary. If possible, the pipeline
should be of one size and laid out so as to contain a
minimum number of bends.
c. Mixture proportions. Concrete mixture proportions
of pumpable mixtures are essentially the same as those to be
placed by other methods, except that more emphasis should
be placed on the grading of the fine aggregates. Concretes
which are pumped must be cohesive. Harsh mixtures do not
pump well. Pressure exerted by the pump can force the
mortar away from the coarse aggregate causing a blockage
in the line if the mixture is not proportioned properly. The
cement content will generally be somewhat higher for
pumped mixtures than those of mixtures placed by
conventional methods. The higher fine aggregate content
will have a higher water demand, which in turn will require
a higher cement content. However, extra cement should not
be used to correct pumping deficiencies resulting from
poorly graded aggregates. It is usually more preferable to
correct deficiencies in the fine aggregates by blending in
additional fine aggregates or pozzolan than by adding
cement.
d. Coarse aggregates. The nominal maximum size of
the coarse aggregate is limited to one-third of the smallest
inside diameter of the pump line for crushed aggregates or
40 percent of the smallest inside diameter of the pump line
for well-rounded aggregates. Oversize particles should be
eliminated. A higher mortar content will be necessary to
effectively pump a concrete containing crushed aggregates
than for a concrete containing rounded aggregates.
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97. EM 1110-2-2000
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Depending upon the type and size of the coarse aggregate,
it may be necessary to reduce the coarse aggregate content
from 5 to 10 percent as compared to mixtures placed by
conventional methods.
e. Fine aggregate. The properties of fine aggregates
are more critical in proportioning pumpable mixtures than
are the properties of the coarse aggregates. Together with
the cement and water, the fine aggregates constitute the
mortar which conveys the coarse aggregates in suspension
through the pump line. Fine aggregates should conform to
the requirements given in ASTM C 33 (CRD-C 133) for
fine aggregates. In addition, for pump systems having lines
6-in. in diameter and smaller, 15 to 30 percent of fine
aggregate should pass the 300-µm (No. 50) sieve and 5 to
10 percent should pass the 150-µm (No. 100) sieve. Fine
aggregates that are deficient in either of these two sizes
should be blended with selected finer aggregates to produce
the desired grading. Pumpability of concrete is generally
improved with a decrease in the fineness modulus. Fine
aggregates having a fineness modulus between 2.40 and
3.00 are generally satisfactory provided that the percentages
passing the 300- and 150-µm (No. 50 and No. 100) sieves
meet the previously stated guidelines. Fineness modulus
values alone without stipulations on the finer sizes may not
produce satisfactory results. Both manufactured fine
aggregates and natural sands can be used in pumped
mixtures provided their gradings are appropriate; however,
natural sands are preferred due to their rounded shape.
f. Slump. The water requirements to establish the
optimum slump and to maintain control of that slump
throughout the course of a pumping placement are both
extremely important factors. Concretes having slumps less
than 2 in. when delivered to the pump are difficult to pump.
Concretes having slumps over 6 in. can segregate causing a
blockage in the pump line and may require a pump aid to
increase the cohesiveness of the concrete to prevent the
aggregate from separating from the mortar during pumping.
It is much more important to obtain a cohesive concrete
through proper proportioning than to try to overcome
deficiencies by adding extra water. In fact, the use of
excess water creates more problems than it solves.
g. Admixtures. Materials which improve workability,
such as water-reducing, high-range water-reducing, and air-
entraining admixtures, as well as pozzolans, usually improve
pumpability. It is common to experience a decrease in air
content during pumping. The specified air contents required
for durability should be obtained at the point of placement
in the structure. Therefore, it may be necessary to entrain
a higher air content into the concrete mixture prior to
pumping. Pumping aids are admixtures which can reduce
friction, reduce bleeding, and increase cohesiveness, all of
which make concretes pump easier.
h. Pumpability tests. There is no standard laboratory
test method available to accurately test the pumpability of
a concrete mixture. Testing a concrete mixture for
pumpability involves duplicating anticipated job conditions
from beginning to end. A full-scale field test for
pumpability should be considered to evaluate both the
mixture proportions and pumping equipment. Prior use of
a mixture and pumping equipment on another job may
furnish evidence of pumpability if job conditions are
duplicated.
i. Planning. Proper planning of the entire pumping
operation including pump location, line layout, placing
sequence, and concrete supply will result in savings of time
and expense. The pump should be as near the placement
area as possible. Concrete delivery systems should have
easy access to the pump. Lines from the pump to the
placement area should be made up primarily of rigid pipe
and contain a minimum number of bends. For large
placement areas, alternate lines should be laid for rapid
connection when required, and standby power and pumping
equipment should be readily available to replace an initial
piece of equipment should a breakdown occur.
j. Other requirements. When pumping downward 50
ft or more, an air release valve at the middle of the top bend
will prevent vacuum or air buildup. When pumping
upward, a shutoff valve near the pump will prevent the
reverse flow of concrete during the fitting of cleanup
equipment or when working on the pump. Direct
communication should be maintained between the placing
crew and the pump operator. Good communication between
the pump operator and the concrete batch plant is also
important. It is desirable to have the concrete delivery such
that the pumping can proceed continuously. When a delay
occurs, it may be difficult to start the concrete moving in
the line again, especially if the delay has been for a
considerable length of time. This critical delay time will
depend upon such factors as the concrete mixture,
temperature, length of pipeline, and type of pump. It may
be necessary to clean the line and start again if the delay
becomes extended. A grout or mortar should be used to
lubricate the pipeline anytime pumping is started with clean
lines, but it should not be pumped into the forms.
k. Quality verification. A high level of quality control
must be maintained to provide assurance that the concrete
is of the desired quality. Concrete should be sampled at
both ends of the pumpline to determine what, if any,
changes in the slump, air content, and other concrete
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properties occur during pumping. However, the quality of
the concrete being placed in the structure can only be
measured at the placement end of the pumpline.
10-7. Fiber-Reinforced Concrete
a. General. Fiber-reinforced concrete (FRC) is
concrete which contains dispersed, randomly oriented fibers.
Fiber-reinforced concrete and fiber-reinforced shotcrete have
been used for pavements, overlays, patching, floor slabs,
refractory materials, hydraulic structures, thin shells, armor
for jetties, rock slope stabilization, tunnel linings, and
precast units since the mid 1960’s. Fibers have been
produced from steel, plastic, glass, and natural materials in
various shapes and sizes. ASTM A 820 (CRD-C 539) is the
specification which covers minimum standards for steel
fibers intended for use in fiber-reinforced concrete. The
size of fibers are usually described by their aspect ratio,
which is the fiber length divided by an equivalent fiber
diameter. Aspect ratios typically range from about 30 to
150. Some steel fibers are collated with water-soluble glue
into bundles of 10 to 30 fibers to facilitate handling and
mixing. Uniform dispersion of fibers through the concrete
provides isotropic strength properties not common to
conventionally reinforced concrete. Additional information
on steel FRC may be found in ACI 544.1R, ACI 544.2R,
ACI 544.3R, and ACI 544.4R.
b. Advantages and limitations. Steel fibers increase
the first crack flexural strength, direct tensile strength, and
splitting tensile strength. Compressive strengths may exhibit
a minor increase. Fibers can increase the ductility of
concrete substantially depending on the type and amount of
fiber present in the concrete. However, balling of fibers in
the mixer hinders uniform distribution and reduces
workability. This can impose an upper limit beyond which
benefits gained from the fibers are no longer realized. This
upper limit depends upon the type and size of fibers and the
mixing procedures being used. Because of mixing and
placing considerations, approximately 2 percent by volume
of the total concrete mixture is considered the practical
upper limit for most types of fibers in field placements.
Higher percentages could be used when the fibers are a type
that do not interlock significantly. However, fibers with
hooked ends can achieve essentially the same properties as
straight fibers of the same aspect ratio using less fiber.
c. Toughness. Steel fibers increase the toughness,
which is a measure of the energy absorption capacity of
concrete. The increase in toughness depends on the type,
amount, and aspect ratio of the fibers. In general, crimped
fibers, surface-deformed fibers, and fibers with hooked ends
produce toughness indexes greater than those for smooth
straight fibers at the same volume concentration.
d. Performance characteristics. Steel fiber concrete
has shown good resistance to dynamic forces and a
significant increase in fatigue strength. Fatigue strength
tends to increase with an increase in fiber loading, and the
crack width under fatigue loading tends to decrease. The
benefits that a conventional concrete mixture gains from
steel fibers depend primarily on the loading of fibers and the
size, shape, and aspect ratio of the fibers. Steel-fiber
concrete has not shown excessive corrosion of the steel
fibers when placed in corrosive environments. The
corrosion has been confined to the fibers actually exposed
to the surface. Fiber-reinforced concrete has shown good
resistance to cavitation forces resulting from high-velocity
water flow and to the damage caused by the impact of large
waterborne debris at high velocity. However, FRC exhibits
poor resistance to abrasion that occurs from the grinding
action of rocks and debris carried in low-velocity water.
Therefore, FRC shall not be used in areas subject to
underwater abrasion.
e. Mixture proportioning. Fiber-reinforced concrete
generally has higher cement and fine aggregate contents and
smaller NMSA than conventional concrete. Coarse
aggregates are generally 19.0-mm (3/4-in.) nominal
maximum size or smaller. Pozzolans are often used to
reduce the relatively high cement contents. Chemical
admixtures are commonly used for air-entrainment, water
reduction, and workability improvement. To ensure uniform
mixing, the maximum aspect ratio of round wire and flat
strip fibers should be no greater than 100.
Characteristically, an FRC mixture will experience a
decrease in workability as the fiber loading increases.
Experience suggests w/c between 0.40 and 0.60 and
cementitious contents between 500 and 900 lb/yd3
are
required when steel fibers are used to produce adequate
paste to coat the large surface area of the fibers. The
percentage of fine aggregate to total aggregate will range
from 45 to 60 percent depending on the NMSA and
aggregate gradings. Once mixture proportions have been
developed, a full-size trial batch should be produced in the
plant and mixer to be used for the project prior to the actual
placement of the fiber-reinforced concrete.
f. Batching and mixing. Mixing of FRC can be
accomplished by different methods, depending on the job
requirements and the facilities that are available. The
ultimate goal is to have a uniform dispersion of the fibers
and prevent the segregation or balling of the fibers during
mixing. Segregation or balling of the fibers is related to
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several factors, the most important of which appears to be
the aspect ratio. Other factors such as the fiber loading,
coarse aggregate size, aggregate grading, w/c ratio, and
method of mixing can also influence the fiber distribution.
Increases in aspect ratio, fiber loading, coarse aggregate
size, and quantity of coarse aggregate intensify balling
tendencies. Most fiber balling occurs as the fibers are
added to the concrete mixture and can be eliminated by
controlling the rate of fiber addition or by the use of
collated fibers. If collated fibers are used, they may be
dumped directly into the concrete mixture as the last step.
Subsequent mixing action separates and disperses the fibers
throughout the mixture. If loose fibers are used, they must
be added slowly and uniformly to the mixture in such a way
as to prevent large clumps of fibers from entering the
mixture. The fibers can be added to the aggregates prior to
introduction of the cement and water or as the last step.
The method of introducing the fiber into the mixture should
be tried in the field during a trial mixture. Fiber balling that
occurs after fiber addition can usually be attributed to
overmixing or poor mixture proportions, such as too much
coarse aggregate or a fiber loading that is too high.
g. Placement. A fiber-reinforced concrete mixture will
generally require more effort to move and consolidate into
forms. The fibrous nature of the mixture makes the use of
shovels or hoes difficult. Forks and rakes are preferred for
handling low-slump mixtures. Properly controlled internal
vibration is acceptable, but external vibration of the forms
and exposed surface is preferable to prevent fiber
segregation. Standard finishing and curing methods can be
used with FRC with one exception. If a textured surface is
desired, a burlap drag is not recommended as the fibers can
hang up in the burlap. A textured surface can be obtained
by brooming with a stiff brush, but it should be delayed as
long as possible to prevent pulling fibers to the surface.
h. Workability. The inverted slump cone test,
described in ASTM C 995 (CRD-C 67), should be used as
an indicator of workability of FRC. The advantage of the
inverted slump cone test over the slump test is that it takes
into account the mobility of concrete which comes about
because of vibration. Reliance on the slump test often
results in the use of excessive amounts of water in an
attempt to increase the slump without improving
workability.
i. Pumping. Fiber-reinforced concrete with fiber
loadings up to 1.5 percent by volume of the total mixture
have been pumped using 5- to 6-in.-diam pipelines. Steel
FRC can be produced using conventional shotcrete
equipment.
j. Other fibers. Glass fibers are subject to chemical
attack by the alkalinity of the concrete, become brittle, and
lose their effectiveness over a period of time. Nylon,
polypropylene, and polyethylene fibers are not subject to
chemical attack. Polypropylene fibers are available in
several forms, such as smooth monofilaments, fibrillated
monofilaments, fibrillated mesh, and collated fibrillated
mesh. Properties of polypropylene FRC can vary somewhat
depending upon the type of fiber used. Incorporation of
polypropylene fibers into concrete can result in a small
improvement in flexural and tensile strengths; however,
these improvements are not always evident. Compressive
strengths can be either increased or decreased. Fracture
toughness can be increased, and shrinkage can be decreased.
k. Effects of polypropylene fibers on
workability. Polypropylene fibers also affect the rheological
properties of fresh concrete. Slump decreases as the volume
concentration of fibers increases. The slump of a typical
concrete can decrease by as much as 50 percent with the
addition of 0.10 percent polypropylene fibers. Bleeding can
be significantly reduced in polypropylene FRC.
l. Use of polypropylene fibers. Polypropylene FRC is
typically used in nonload-bearing applications particularly
where impact resistance is important. The use of
polypropylene fibers for control of cracking in slabs is still
being debated due to the amount of fibers required to
positively affect the amount of cracking and the subsequent
effect on workability.
10-8. Porous Concrete
a. General. Porous concrete is commonly used where
either free drainage is required or where lower mass and
lower thermal conductivity are required. The use of
lightweight aggregates is not practicable or desired. It is
normally produced by binding a gap-graded or a single-size
aggregate with a cement paste. The structure of the material
permits the passage of water but also provides moderate
structural strength. Porous concrete has been used for drain
tiles, drains beneath hydraulic structures to relieve uplift
pressures, pavement edge drains, etc.
b. Types. At least three distinct types of porous
concretes can be produced. These include cellular concretes
made by introducing a preformed foam into the fresh mortar
or causing the creation of gas bubbles in the mortar due to
a chemical reaction; lightweight aggregate concrete made
with natural or synthetic aggregates which are often
extremely porous; or concrete which uses gap-graded or
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single-size aggregate and typically totally eliminates the fine
aggregate fraction from the mixture (no-fines concrete).
While each of these concretes are porous, they possess
differing void structures. Cellular and lightweight aggregate
concretes may contain large percentages of voids, but these
voids are relatively noncommunicating. Porous concretes
produced by intentional gap grading or without fine
aggregate can result in concrete with high percentages of
interconnected voids. The porous concretes with
noncommunicating voids may absorb small amounts of
moisture, but they do not allow rapid passage of water
through the concrete. For this reason cellular and
lightweight concretes should not normally be considered for
the porous concrete applications previously noted and are
not discussed in further detail.
c. Composition. Porous concrete is composed of
coarse aggregate, cementitious material, and water.
Occasionally, a small amount of fine aggregate can be used
to increase the compressive strength and to reduce
percolation. The coarse aggregate should comply with
ASTM C 33 (CRD-C 133) size designations No. 8 (9.5-mm
(3/8-in.) NMSA), No. 7 (12.5-mm (1/2-in.) NMSA), or No.
67 (19.0-mm (3/4-in.) NMSA). Both rounded and crushed
aggregates have been used to produce porous concrete.
d. W/C considerations. The w/c of a porous concrete
mixture is important to achieve the specified strength and to
help create the proper void structure. A high w/c reduces
the cohesion of the paste to the aggregate and causes the
paste to flow downward and blind the void structure when
the mixture is even lightly compacted. If the w/c is too
low, balling will occur in the mixture, and the materials will
not be evenly distributed throughout the batch. Experience
indicates that the w/c should fall within a range of 0.35 to
0.45 for the paste to be stable and provide the best
aggregate coating. The w/c - compressive strength
relationship which is normally associated with conventional
concrete does not apply to porous concrete.
e. Durability. The frost resistance of porous concrete
is acceptable if the bonding paste is air entrained. However,
because of the interconnected void system and high surface
area of exposed paste in porous concrete, resistance to
aggressive attack by sulfates and acids that may percolate
through this concrete is questionable.
f. Percent voids. The percent voids, expressed as the
air content, should be determined in accordance with ASTM
C 138 (CRD-C 7). The air content should be 15 percent or
greater, by volume, to ensure that water will percolate
through porous concrete. The compressive strength of
porous concrete will range from approximately 3,500 psi at
28-days age when the air content is 15 percent to
approximately 1,500 psi when the air content is 25 percent.
The percolation rate is proportional to the air content of
porous concrete while the compressive strength is inversely
proportional. The compressive strength also increases as the
NMSA decreases.
g. Proportioning porous concrete mixtures. Although
no ACI guidance for proportioning porous concrete currently
is available, research conducted by the National Aggregates
Association-National Ready Mixed Concrete Association
(Meininger 1988) indicates that the dry-rodded unit weight
of coarse aggregate as determined by ASTM C 29 (CRD-C
106) can be effectively used to proportion porous concrete.
This approach to proportioning uses the b/bo concept
discussed in CRD-C 99 for proportioning normal weight
concrete. The ratio b/bo compares the amount of coarse
aggregate in a unit volume of concrete with the amount of
coarse aggregate in a like volume of dry-rodded coarse
aggregate. This method automatically compensates for the
effects of different coarse aggregate particle shape, grading,
and density. Also, the b/bo values for a range of NMSA
normally used in porous concrete (9.5 to 19.0 mm (3/8 to
3/4 in.)) are very similar.
h. Placement. Proper construction methods are critical
to the performance of porous concrete. Some compaction
is needed during placement and the coarse aggregate on the
top surface needs to be properly seated to reduce ravelling
of the surface. Small steel wheel rollers have been used
with some success for compaction. Curing is very
important since porous concrete can dry very rapidly.
Curing is vital to the continued hydration of the top surface.
The level of compaction should be considered in the mixture
proportioning study. If the porous concrete is compacted
too much, the void content may be reduced below 15
percent, and flow channels will be plugged. Too little
compaction will cause the concrete to have a very high void
content and will result in low strength. Test specimens
should be compacted to the same density as will be obtained
in the field. This may require some experimentation in the
laboratory to obtain comparable compaction in the field and
the laboratory.
10-9. Flowing Concrete
a. General. Flowing concrete is defined by ASTM C
1017 (CRD-C 88) as "concrete that is characterized as
having a slump greater than 7-1/2-in. while maintaining a
cohesive nature." It can be placed to be self-leveling, yet
remaining cohesive without segregation, excessive bleeding,
or extended retardation. Flowing concrete can be used in
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congested areas where members are reinforced or unusually
shaped or in areas of limited access. Flowing concrete
pumps easily, and therefore, the concrete pumping distance
and rate are increased. Proper consolidation around
reinforcement is more easily achieved with flowing concrete
than normal-slump concrete, and less vibration is required.
Proper vibration is necessary for complete consolidation and
bond to reinforcing steel.
b. HRWRA. Flowing concrete is produced by the
addition of a normal (Type I) or a retarding (Type II)
HRWRA, as described by ASTM C 1017 (CRD-C 88).
These admixtures are generally identical to those described
by ASTM C 494 (CRD-C 87) as HRWRA’s, Types F and
G, respectively. Flowing concrete cannot be produced by
the addition of water since it will lose the cohesiveness
necessary to minimize segregation. The amount of
HRWRA required to produce flowing concrete varies
depending upon the cement type, w/c, initial slump,
temperature, time of addition, concrete mixture proportions,
and the type of admixture. Concretes having lower initial
slumps generally require larger amounts of HRWRA to
produce flowing concrete than do concretes having higher
initial slumps. HRWRA are also generally more effective
in concrete having higher cementitious material contents.
c. Proportioning flowing concrete. Mixture
proportions for flowing concrete usually contain more fine
material than a conventional concrete mixture. This is
necessary to achieve a flowable consistency without
excessive bleeding or segregation. The fine aggregate
content is usually increased by 3 to 5 percent, and in some
cases, an increase in cement or pozzolan may be necessary.
Since HRWRA’s are usually added in large volumes, the
water in the admixture must be accounted for in calculating
w/c and yield. Higher dosages of air-entraining admixture
are usually required to maintain proper air content in
flowing concrete. The air content should be monitored
regularly at the point of discharge into the forms so that the
dosage of air-entraining admixture can be adjusted as
necessary to maintain the air content within the specified
range. The slump should be measured prior to addition of
the HRWRA to assure that an excessive amount of water
has not been added to the batch. After the HRWRA is
added and thoroughly mixed into the concrete, the resulting
slump should be within the specified range.
d. Flowing concrete fresh properties. Flowing
concretes may exhibit a rapid slump loss depending on a
variety of factors. Concrete temperature, cement
composition, and cement content will influence the rate of
slump loss. Also, flowing concrete made with plasticizing
admixtures can lose much of its slump in as few as
30 minutes. Plasticizing admixtures must be measured
accurately and discharged onto the concrete properly
regardless of where their addition occurs. Additional
dosages of HRWRA can be used when delays occur and
slump is lost. Up to two additional dosages have been used
successfully. In general, the compressive strength is
unchanged, but the air content is decreased with additional
dosages of HRWRA. The characteristics of flowing
concrete at the time of finishing should be similar to that of
conventional concrete with the same materials. Properly
proportioned flowing concrete should not exhibit
objectionable bleeding. As with the finishing of
conventional concrete, proper timing of each finishing
operation is imperative.
e. Flowing concrete hardened properties. The
compressive strength, flexural strength, drying shrinkage,
creep, and permeability of flowing concrete is not
significantly different than that of lower slump concrete
having the same w/c and air content. The air-void system
may have larger bubble spacing factors and a decrease in
the number of voids per inch compared to the initial
concrete, yet satisfactory frost resistance is still achieved in
most cases.
10-10. Silica-Fume Concrete
a. General. The use of silica fume as a pozzolan in
concrete produced in the United States has increased in
recent years. When properly used, it can enhance certain
properties of both fresh and hardened concrete including
cohesiveness, strength, and durability. Silica-fume concrete
may be appropriate for concrete applications which require
very high strength, high abrasion resistance, very low
permeability, or where very cohesive mixtures are needed to
avoid segregation.
b. Properties of silica fume. Silica fume is a by-
product of fabrication of silicon or ferrosilicon alloys. It is
a very fine powder having a medium to dark gray color. It
is available as loose powder, densified powder, slurry, and
in some areas as a blended portland-silica-fume cement.
Silica-fume particles are spherical and are typically 100
times smaller than portland-cement grains. It typically has
an SiO2 content of 85 to 98 percent. It appears that
concretes benefit from both the pozzolanic properties of
silica fume as well as from the extremely small particle size.
Silica fume is generally proportioned as an addition, by
mass, to the cementitious materials and not as a substitution
for any of those materials.
c. Effect on water demand and bleeding. Silica fume
has a great affinity for water because of its high surface
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area, and this is reflected in the concrete which contains it.
The increased water demand of concrete containing silica
fume can be overcome with the use of a WRA or HRWRA
and to a lesser extent by reducing the fine aggregate content
of the mixture. Silica-fume concrete exhibits less bleeding
than conventional concrete because the high affinity of silica
fume for water results in very little water left in the mixture
for bleeding. Silica-fume particles attach themselves to
adjacent cement particles and reduce the available channels
for bleeding.
d. Effect on cohesiveness. Concrete containing silica
fume is more cohesive and less prone to segregation than a
comparable mixture without fume; however, it also tends to
lose slump more rapidly. Silica-fume additions greater than
10 percent should generally be avoided because the resulting
concrete mixture will become "sticky" and require more
vibration for proper consolidation. A slump increase of
approximately 2 in. may be necessary to overcome this
problem and to maintain the same consistency for some
length of time. On the other hand, some increase in
cohesiveness is an advantage in both flowing and pumped
concretes.
e. Effect on air entrainment. The dosage of AEA
required to produce a particular air content in concrete
increases significantly with increasing amounts of silica
fume. The amount of AEA needed in silica-fume concrete
to entrain a specified amount of air may be as much as five
times greater than that required for similar concrete without
fume. It may also be difficult to entrain more than 5
percent air in concrete containing high silica-fume contents.
f. Effect on plastic shrinkage. When the curing
conditions allow a faster rate of evaporation of water from
the surface of fresh concrete than the water replaced by
bleeding from the concrete underneath, plastic shrinkage
cracking will occur. Therefore, all admixtures and
pozzolans which reduce bleeding of fresh concrete make it
more prone to plastic shrinkage cracking. This is
particularly true for silica-fume concrete in which bleeding
is significantly reduced. The problem can become very
serious under curing conditions of high temperature and
high wind velocity which favor faster evaporation of water
from fresh concrete surfaces. A light fog spray of water can
be used to keep surfaces from drying between finishing
operations, or a sheet material can be used to cover the
surface. Moist curing should begin immediately after
finishing and should continue for a minimum of 14 days.
g. Effect on strength and modulus of elasticity.
Strength development characteristics of silica-fume concrete
are similar to those of fly ash except that the results of the
pozzolanic reactions of silica fume are evident at early ages.
This is because silica fume is a very fine material with a
very high glass and silica content. However, since silica
fume increases the water demand of a mixture, use of a
WRA or HRWRA to offset water demand is necessary to
take full advantage of silica fume’s full potential for
increasing strength. The ratio of flexural to compressive
strength of silica-fume concrete follows the same pattern as
conventional concrete. There are no significant differences
between the Young’s modulus of elasticity of concrete with
and without silica fume. However, very high-strength
concretes tend to be more brittle, and this is also true of
high-strength silica-fume concrete.
h. Effect on permeability and durability. Pozzolans
and GGBF slag often significantly reduce the permeability
of concrete due to their influence on the fine pore structure
and interfacial effects. Silica fume is a much more efficient
pozzolanic material than natural pozzolans or fly ash, and
therefore, it decreases concrete permeability dramatically.
However, silica-fume concrete must still be properly air-
entrained if it is subject to critical saturation and repeated
cycles of freezing and thawing. Silica-fume concretes have
exhibited reduced chloride-ion permeability, enhanced
resistance to attack from sulfates and other aggressive
chemicals, and enhanced abrasion resistance. While
abrasion resistance is more dependent upon the hardness of
the aggregate than upon that of the paste, the addition of
silica fume can increase the abrasion resistance of concrete
when hard aggregates are unavailable or cannot be
economically justified, and inferior aggregates must be used.
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Chapter 11
Concrete Report
11-1. General
a. Policy. A concrete report will be completed at the
conclusion of construction on any major concrete structure
such as a concrete dam, lock, or any project that is unique
or unusual. The specific requirements for concrete report
are outlined in ER 1110-2-402, "Concrete Reports." The
concrete report will serve the dual purpose of meeting the
requirements of ER 1110-2-100, "Periodic Inspection and
Continuing Evaluation of Completed Civil Works
Structures," for engineering data retained at the project site
and advancing the state of the art of constructing large
concrete structures by providing personnel working on
subsequent projects with a discussion of problems
encountered and solutions devised.
b. Author. The concrete report should be completed
by personnel who are familiar with the project preferably
the concrete engineer assigned to the project. Personnel
from the engineering division should contribute to the report
in any areas where they have special knowledge.
c. Timing. The report should be written as the project
progresses so that important information is not lost as
personnel changes occur. The report should be completed
within 120 days of substantial completion of concrete
placing.
11-2. Content
a. Outline. The concrete report should be written to
fulfill the objectives of providing information to those who
may investigate problems with concrete on the project in the
future, those embarking on the design of a similar project,
or those periodically inspecting the project. The concrete
report should include discussions of problems encountered
in each phase of concrete production and placement,
including the production of aggregates. The solutions to
these problems should be summarized. The typical outline
provided in Table 11-1 should serve as a guide in the
preparation of the concrete report.
b. Detailed instruction. The information to be
included in the concrete report are discussed in accordance
with the outline listed in Table 11-1.
(1) Introduction. The introduction of the report should
state the purpose of the report, its scope, and the authority
for the document in accordance with ER 1110-2-402,
"Concrete Reports" In addition, the report should include a
project description and a location and vicinity map to serve
as a guide independent of other project documents. The
introduction should also include a summary table of the
quantities of each major type of concrete on the project, i.e.
interior mass, exterior mass, structural, tremie, backfill, etc.
(2) Aggregate sources. Each aggregate source used
for concrete on the project should be provided by name,
coordinates, and/or street or township of the pit or quarry.
If test data are available in TM 6-370 (USAEWES 1953),
the volume, area, and index numbers should be provided.
Drawings or photographs should be provided to indicate the
exact location within the pit or quarry from which the
aggregate was produced.
(3) Aggregate production.
(a) Pit or quarry operation. This section discusses the
removal of material from the pit or quarry including the
make, model, and capacity of the primary equipment. In
case of a quarry, the most commonly used blasting pattern
should be detailed to include blast hole spacing and depth,
powder types and requirements, and powder factor.
Photographs should be used to the maximum extent to show
the equipment and operation.
(b) Fine aggregate production. Photographs and a
flow chart should be included showing the sequential
processing of the fine aggregate. The major equipment used
in the fine aggregate production should be listed by make,
model, and capacity.
(c) Coarse aggregate production. Photographs and a
flow chart should be included showing the sequential
processing of the coarse aggregate. The major equipment
used should be listed by make, model, and capacity. The
particle shape should be discussed. In this regard, closeup
photographs of the various stockpiles are most helpful.
Readily visible and identifiable objects such as pens,
hardhats, or rules should be placed nearby to provide scale.
If spray bars or wood pickers are required, this should be
noted.
(d) Stockpiling and handling. The number of
stockpiles and the sizes of aggregate in each stockpile
should be noted. The approximate size of the stockpile
during normal aggregate production and concrete placing
should be noted. Photographs or drawings are preferred for
this purpose. If a stockpile was reduced to a very low level
during the placing of concrete, the time of this occurrence
should be noted. The equipment used to move aggregate to
and from the stockpile should be noted.
11-1

104. EM 1110-2-2000
1 Feb 94
Table 11-1
Concrete Report - Typical Outline
1. Introduction.
a. Purpose, scope, and authority
b. Project description
c. Concrete quantities by type
d. List of responsible personnel
2. Aggregate sources
a. General
b. Properties of sources used
3. Aggregate production
a. Pit or quarry operation
b. Fine aggregate production
c. Coarse aggregate production
d. Stockpiling and handling
4. Cementitious materials
a. Portland cement sources
b. Blended hydraulic cement sources
c. Pozzolan sources
d. GGBF slag
e. Silica fume
5. Chemical admixtures
a. Air-entraining admixtures
b. Water-reducing admixtures
c. Retarding admixtures
d. Accelerating admixtures
e. Others
6. Concrete batching and mixing plant(s)
7. Concrete mixtures used
a. Mass concrete
b. Structural concrete
c. Special concrete (RCC, fiber reinforced)
d. Shotcrete
8. Construction joint preparation
11-2

105. EM 1110-2-2000
1 Feb 94
Table 11-1 (Continued)
9. Concrete transportation, placement, and consolidation
a. Concrete transportation
b. Concrete placement
c. Shotcrete placement
d. Concrete placing schedule
e. Concrete consolidation
10. Concrete curing and protection
11. Temperature control
a. Insulation
b. Precooling
c. Postcooling
d. Heating
12. Special concretes
a. Fiber-reinforced concrete
b. Roller-compacted concrete
c. Tremie concrete placed in cutoff walls
d. Tremie concrete in underwater applications
e. Other unusual applications of material or means of placement
13. Precast concrete
14. Quality verification and testing
a. Government quality verification
b. Laboratory facilities
15. Summary of test data
a. Aggregate quality tests
b. Aggregate grading tests
c. Tests of cementitious materials
d. Tests of admixtures
e. Concrete strength tests
f. Concrete F/T tests
g. Air content tests
h. Slump tests
i. Placing temperature
j. Resistance thermometer data
16. Special problems
a. Problem
b. Actions
c. Comments
11-3

106. EM 1110-2-2000
1 Feb 94
(4) Cementitious materials.
(a) Portland cement sources. The sources of portland
cement used on the project should be noted as well as the
dates they were used and the approximate locations of their
use. The means of transporting the cement to the project
site should be noted and the transfer and storage facilities
described.
(b) Blended hydraulic cement sources. If blended
hydraulic cement is used on the project, it should be
discussed as described for portland cement in the previous
paragraph.
(c) Pozzolan source. The sources of pozzolan used on
the project should be listed. If commercial sources are used,
the location of the firms supplying the pozzolan should be
listed. If a source of natural pozzolan is developed and
used by the Contractor or if a natural source is opened
nearby by a commercial operator to supply pozzolan to the
project, the location of the source should be provided and
the processing requirements outlined.
(d) GGBF slag or silica fume. The sources of GGBF
slag or silica fume, or both, if used, should be listed.
Storage, handling, and batching facilities should be
described. If they were used only in certain locations in the
structures, the locations, dates placed, and mixture
proportions should be included.
(5) Chemical admixtures. The brand name, sources,
and available test data of all chemical admixtures used on
the project should be listed as well as the structure feature
in which they were used.
(6) Concrete batching and mixing plant. The concrete
batching and mixing plant should be described to include
make, model, and capacity of major bins, conveyor belts,
hoppers, mixers, and controls. Photographs of the overall
plant layout should be included.
(7) Concrete mixtures used. The proportions of the
concrete mixtures used during the bulk of the placement of
each major class of concrete should be tabulated. The
aggregate batch weights should be reported at saturated
surface dry. If significant field adjustments were made to
the concrete mixtures that were supplied by the division
laboratory being placed in a dam, power plant, lock, or
other major water control structures, the extent of the
adjustment should be noted and reasons for the adjustment
discussed. If shotcrete is used on the project, the type of
placement (wet or dry) should be noted and the type and
capacity of equipment listed.
(8) Equipment and techniques. The equipment and
techniques used for joint preparation should be described.
(9) Concrete transportation and placement. The type
and capacity of equipment used to transport the concrete
from the mixer to the placement site should be described.
The means of placement should be described and the
number and type of vibrators noted. The normal and
maximum rates of placement of each major class of
concrete on the project should be listed.
(10) Concrete curing and protection. A brief
description should be provided outlining the Contractor’s
selected means of curing and protecting the concrete. Any
mishaps which occurred during curing and protection which
may have reduced the level of protection or truncated the
curing process on parts of major structures should be noted.
(11) Temperature control. The description of the
temperature control measures used on the project will
include the types of insulation used, the major components
of any required pre- or postcooling systems, the dates that
various control measures were used during the construction
period, and any mishaps which resulted in deviations from
the specified temperature control requirements.
(12) Special concretes. On any project that includes
concrete different than the usual cast-in-place mass or
structural concrete, a section should be provided detailing
the materials used, the method of placement, problems
encountered, and how they were solved. Concrete
applications which should be discussed include tremie
concrete when placed in a major project element such as a
cutoff wall, underwater foundation, or fiber-reinforced
concrete.
(13) Precast concrete. The type, description, name,
and location of the manufacturer of precast units used on the
project should be provided.
(14) Quality verification and testing. The procedure
and extent of the GQA program and the CQC program
should be described. The types and frequencies of the tests
and quality verifications performed by the Government
should be listed. The facility used by the Government for
GQA purposes and by the Contractor for CQC should be
described.
(15) Summary of test data. The format for the
presentation of data from the various quality assurance tests
and quality control tests should be such that long tables of
raw data are avoided. Charts should be used where
possible. Charts and tables when used should show the
11-4

107. EM 1110-2-2000
1 Feb 94
average of the values presented as well as the extremes and
the specification limits. Use of computer programs for
compiling and analyzing concrete data during construction
is encouraged. The reports generated by these computer
programs may be incorporated into the concrete report with
minimum efforts. It is recommended that complete testing
data stored in disks be included as enclosure for future use.
(16) Special problems. Any unusual problems
encountered during the concrete construction and corrective
actions taken should be described. Any comment or
evaluation of the results should be provided or documented.
11-5

108. EM 1110-2-2000
1 Feb 94
Appendix A
References
A-1. Required Publications
TM 5-822-7
Standard Practice for Concrete Pavements
ER 415-1-11
Biddability, Constructibility, and Operability
ER 1110-1-261
Quality Assurance of Laboratory Testing Procedures
ER 1110-1-2002
Cement, Pozzolan, and Slag Acceptance Testing
ER 1110-1-8100
Laboratory Investigations and Materials Testing
ER 1110-2-100
Periodic Inspection and Continuing Evaluation of Completed
Civil Works Structures
ER 1110-2-402
Concrete Reports
ER 1110-2-1150
Engineering and Design for Civil Works Projects
ER 1110-2-1200
Plans and Specifications
ER 1180-1-6
Construction Quality Management
EM 1110-1-1804
Geotechnical Investigations
EM 1110-2-2002
Evaluation and Repair of Concrete Structures
EM 1110-2-2302
Construction with Large Stone
EP 415-1-261
Quality Assurance Representative’s Guide
CW 03101
Formwork for Concrete
CW 03150
Expansion, Contraction, and Construction Joints in Concrete
CW 03301
Cast-in-Place Structural Concrete
CW 03305
Guide Specification for Mass Concrete
CW 03307
Concrete (for Minor Structures)
CW 03362
Preplaced Aggregate Concrete
CW 03425
Precast-Prestressed Concrete
US Army Engineer Waterways Experiment Station 1949
US Army Engineer Waterways Experiment Station. 1949.
Handbook for Concrete and Cement, with quarterly
supplements (all CRD-C designations), Vicksburg, MS.
Note: Use latest edition of all designations.
US Army Engineer Waterways Experiment Station 1953
US Army Engineer Waterways Experiment Station. 1953.
Test Data, Concrete Aggregates in Continental United States
and Alaska, with annual supplements, Technical Memoran-
dum No. 6-370, Vicksburg, MS.
American Concrete Institute (Annual)
American Concrete Institute. Annual. Manual of Concrete
Practice, Five Parts, Detroit, MI, including:
"Cement and Concrete Terminology," ACI 116R
"Standard Specifications for Tolerances for Concrete
Construction and Materials," ACI 117
"Guide to Durable Concrete," ACI 201.2R
"Cooling and Insulating Systems for Mass Concrete," ACI
207.4R
"Standard Practice for Selecting Proportions for Normal,
Heavyweight, and Mass Concrete," ACI 211.1
"Chemical Admixtures for Concrete," ACI 212.3R
"Recommended Practice for Evaluation of Strength Test
Results of Concrete," ACI 214
"Use of Accelerated Strength Testing," ACI 214.1R
"Guide for Use of Normal Weight Aggregates in Concrete,"
ACI 221R
A-1

109. EM 1110-2-2000
1 Feb 94
"Control of Cracking in Concrete Structures," ACI 224R
"In-Place Methods for Determination of Strength of
Concrete," ACI 228.1R
"Guide for Concrete Floor and Slab Construction," ACI
302.1R
"Guide to Cast-in-Place Architectural Concrete Practice,"
ACI 303R
"Guide for Measuring, Mixing, Transporting, and Placing
Concrete," ACI 304R
"Placing Concrete by Pumping Methods," ACI 304.2R
"Placing Concrete with Belt Conveyors," ACI 304.4R
"Hot Weather Concreting," ACI 305R
"Cold Weather Concreting," ACI 306R
"Standard Practice for Curing Concrete," ACI 308
"Guide for Consolidation of Concrete," ACI 309R
"Building Code Requirements for Reinforced Concrete (ACI
318) and Commentary," ACI 318/318R
"State-of-the-Art Report on High Strength Concrete," ACI
363R
"State-of-the-Art Report on Fiber-Reinforced Concrete,"
ACI 544.1R
"Measurement of Properties of Fiber-Reinforced Concrete,"
ACI 544.2R
"Guide for Specifying, Mixing, Placing, and Finishing Steel
Fiber-Reinforced Concrete," ACI 544.3R
"Design Considerations for Steel Fiber Reinforced
Concrete," ACI 544.4R
American Society for Testing and Materials (Annual)
American Society for Testing and Materials. (Annual).
Annual Book of ASTM Standards, Philadelphia, PA.
Note: Use the latest available issue of each ASTM
Standard.
A-2. Related Publications
ER 415-2-100
Construction Management Policies, Procedures, and Staffing
for Civil Works Projects
ER 1110-1-1804
Geotechnical Investigation
ER 1110-1-8101
Reports of Pertinent Activities at Division Laboratories
EM 1110-1-2009
Architectural Concrete
EM 1110-1-2101
Working Stresses for Structural Design
EM 1110-2-2005
Standard Practice for Shotcrete
EM 1110-2-2006
Roller-Compacted Concrete
American Concrete Institute 1988
American Concrete Institute. 1988. "No-fines Pervious
Concrete for Paving," Concrete International: Design and
Construction, Vol. 10, No. 8, Detroit, MI.
American Society for Testing and Materials 1978
American Society for Testing and Materials. 1978. "The
Significance of Tests and Properties of Concrete and
Concrete-Making Materials," ASTM Special Technical
Publication No. 169B, Philadelphia, PA. (Use 169C when
it appears ~ probably early in 1994.)
Bisque and Lemish 1958
Bisque, R. E., and Lemish, John. 1958. "Chemical Charac-
teristics of Some Carbonate Aggregate as Related to Dura-
bility of Concrete," Highway Research Board Bulletin 196,
Washington, DC, pp 29-45.
Buck 1965
Buck, A. D. 1965 (Jun). "Investigation of a Reaction
Involving Nondolomitic Limestone Aggregate in Concrete,"
Miscellaneous Paper No. 6-724, 38 pp, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, MS.
Buck 1983
Buck, A. D. 1983. "Alkali Reactivity of Strained Quartz as
a Constituent of Concrete Aggregate," Miscellaneous Paper
A-2

110. EM 1110-2-2000
1 Feb 94
SL-83-13, U.S. Army Engineer Waterways Experiment
Station, Vicksburg, MS.
Buck 1988
Buck, A. D. 1988. "Use of Pozzolan or Slag in Concrete
to Control Alkali-Silica Reaction and Sulfate Attack,"
Technical Report SL-88-29, U.S. Army Engineer Waterways
Experiment Station, Vicksburg, MS.
Bureau of Reclamation 1975
Bureau of Reclamation. 1975. Concrete Manual 8th
edition. For sale by Superintendent of Documents, US
Government Printing Office, Washington, DC 20402.
Canadian Standards Association 1986
Canadian Standards Association. 1986 (Oct). "Potential
Expansivity of Cement Aggregate Combinations (Concrete
Prism Expansion Method)," CAN3-A23.2-M77, A23.2-14A,
Supplement No. 2.
Diamond 1976
Diamond, S. 1976. "A Review of Alkali Silica Reaction
and Expansion Mechanisms: 2. Reactive Aggregates,"
Cement and Concrete Research, Vol 6, pp 549-560.
Diamond 1978
Diamond, S. 1978. "Chemical Reactions Other Than
Carbonate Reactions," Chapter 23, ASTM Special Technical
Publication 169B, pp 700-721.
Dolar-Mantuani 1983
Dolar-Mantuani, L. 1983. Handbook of Concrete
Aggregates,Chapter 7, "Alkali-Aggregate Reactivity," Noyes
Publications, Park Ridge, NJ, pp 79-125.
Grattan-Bellew 1987
Grattan-Bellew, P. E., ed. 1987. "Concrete Alkali-
Aggregate Reactions, Proceedings 7th International
Conference, Noyes Publications, Park Ridge, NH, 509 pp.
Grattan-Bellew 1992
Grattan-Bellew, P. E. 1992. "Microcystalline Quartz,
Undulatory Extinction & the Alkali-Silica Reaction,"
Proceedings 9th International Conference, The Concrete
Society, Slough, Vol 1, pp 383-394.
Hadley 1961
Hadley, David W. 1961. "Alkali Reactivity of Carbonate
Rocks--Expansion and Dedolomitization," Proceedings,
Highway Research Board, Vol 40, pp 462-474, 664 pp.
Hadley 1968
Hadley, David W. 1968. "Field and Laboratory Studies on
the Reactivity of Sand-Gravel Aggregate," Journal of PCA
R&D Labs, PCA Research Bulletin No. 221, Vol 10, No. 1
pp 17-33.
Highway Research Board 1964
Highway Research Board. 1964. "Symposium on Alkali-
Carbonate Rock Reactions," Highway Research Record
No. 45 , HRB Publication 1167, 244 pp.
Kosmatka and Panarese 1988
Kosmatka, Steven H., and Panarese, William C. 1988.
Design and Control of Concrete Mixtures, 13th ed., Portland
Cement Association, Skokie, IL.
MacInnis 1992
MacInnis, Cameron. 1992. "Guide to Durable Concrete,"
ACI Committee Report 201.2R-92, ACI Manual of Concrete
Practice, Part I, American Concrete Institute, Detroit, MI.
Mather 1948
Mather, Bryant. 1948. "Petrographic Identification of
Reactive Constitutents in Concrete Aggregate," Proceedings,
American Society for Testing Materials, Vol 48, pp 1120-
1125.
Mather, K. et al 1963
Mather, Katharine; Luke, Wilbur I.; and Mather, Bryant.
1963 (Jun). "Aggregate Investigations, Milford Dam,
Kansas; Examination of Cores from Concrete Structures,"
Technical Report No. 6-629, 81 pp, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, MS.
Meininger 1988
Meininger, Richard C. 1988 (Aug). "No-Fines Pervious
Concrete for Paving," Concrete International, American
Concrete Institute, Vol 10, No. 8.
Mielenz 1958
Mielenz, R. C. 1958. "Evaluation of the Quick-Chemical
Test for Alkali Reactivity of Concrete Aggregate," Highway
Reserch Bulletin No. 171, pp 1-15.
Mindess and Young 1981
Mindess, Sidney, and Young, J. Francis. 1981. Concrete,
Prentice-Hall, Englewood Cliffs, NJ.
Natesaiyer and Hover 1985
Natesaiyer, K., and Hover, K. 1985. "Insitu Identification
of ASR Products in Concrete," Cement and Concrete
Research, Vol 18, pp 455-463.
National Ready-Mixed Concrete Association 1982
National Ready-Mixed Concrete Association. 1982 (Sep).
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111. EM 1110-2-2000
1 Feb 94
Concrete Plant Standards of the Concrete Plant Manu-
facturers Bureau, 8th revision, Spring Street, Silver Spring,
MD (also available as CRD-C 514).
Neeley 1988
Neeley, Billy D. 1988 (Apr). "Evaluation of Concrete
Mixtures for Use in Underwater Reapirs," Technical Report
REMR-CS-18, U.S. Army Engineer Waterways Experiment
Station, Vicksburg, MS.
Neville 1981
Neville, Alan M. 1981. Properties of Concrete, 3rd Edition,
Pitman Publishing, Marshfield, MA.
Oberholster and Davies 1986
Oberholster, R. E., and Davis, G. 1986. "An Accelerated
Method for Testing the Potential Alkali Reactivity of
Siliceous Aggregates," Cement and Concrete Research,
Vol 16, pp 181-189.
Pepper 1953
Pepper, Leonard. 1953. "Tests for Chemical Reactivity
Between Alkalies and Aggregate; QuickChemical Test,"
Technical Memorandum No. 6-368, Report 1, U.S. Army
Engineer Waterways Experiment Station, Vicksburg, MS.
Poole, McLachlan, and Ellis 1988
Poole, A. B., McLachlan, A., and Ellis, D. J. 1988. "A
Simple Staining Technique for the Identification of Alkali-
Silica Gel in Concrete and Aggregate," Cement and
Concrete Research, Vol 18, pp 116-120.
Porter 1978
Porter, L. C. 1978. "A 25-Year Evaluation of Concrete
Containing Reactive Kansas-Nebraska Aggregates, Report
REC-ERC-78-5, Engineering Research Center, Bureau of
Reclamation, Denver, CO.
Saucier 1980
Saucier, Kenneth L. 1980. "High-Strength Concrete, Past,
Present, Future," Concrete International, American Concrete
Institute, Vol 2, No. 6, pp 46-50.
Stark 1983
Stark, David. 1983. "Osmotic Cell Tests to Identify
Potential for Alkali-Aggregate Reactivity," Proceedings, 6th
International Conference on Alkalies in Concrete,
Copenhagen.
Stark 1991
Stark, David. 1991. "Handbook for the Identification of
Alkali-Silica Reactivity in Highway Structures,"
SHRP-C/FR-91-101, Strategic Highway Research Program,
Washington, DC, 49 pp.
Tye and Mather 1956
Tye, R. V., and Mather, Bryant. 1956. "Tests for Chemical
Reactivity Between Alkalies and Aggregate: Mortar-Bar
Test," Technical Memorandum No. 6-368, Report 2, U.S.
Army Engineer Waterways Experiment Station, Vicksburg,
MS.
Tynes et al. 1966
Tynes, W. O., Luke, W. I., and Houston, B. J. 1966.
"Results of Laboratory Tests and Examinations of Concrete
Cores, Carlyle Reservoir Spillway, Carlyle, Illinois,"
Miscellaneous Paper No. 6-802, 29 pp, U.S. Army Engineer
Waterways Experiment Station, Vicksburg, MS.
Waddell 1974
Waddell, Joseph J. 1974. Concrete Construction
Handbook, 2nd edition, McGraw-Hill, New York.
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112. EM 1110-2-2000
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AppendixAppendix BB
AbbreviationsAbbreviations
ACI . . . . . . . . . . . . . . American Concrete Institute
AEA . . . . . . . . . . . . . air-entraining admixture
AHV . . . . . . . . . . . . . Class A, High Velocity
ASTM . . . . . . . . . . . . American Society for Testing
and Materials
AWA . . . . . . . . . . . . . antiwashout admixture
BCO . . . . . . . . . . . . . bidability, constructability,
and operability
CE . . . . . . . . . . . . . . . Corps of Engineers
CECW-EG . . . . . . . . . Geotechnical and Materials
Engineering Branch, Civil
Works Directorate, Headquar-
ters U.S. Army Corps of
Engineers
CEWES-SC . . . . . . . . U.S. Army Engineer Water
ways Experiment Station,
Structures Laboratory, Con-
crete Technology Division
CONUS . . . . . . . . . . . Continental United States
CQC . . . . . . . . . . . . . contractor quality control
CSA . . . . . . . . . . . . . . Canadian Standards Association
CW . . . . . . . . . . . . . . civil works
DM . . . . . . . . . . . . . . design memorandum
DFE . . . . . . . . . . . . . . durability factor (based on
relative dynamic modulus of
elasticity)
EPA . . . . . . . . . . . . . . Environmental Protection
Agency
FCSA . . . . . . . . . . . . . Feasibility Cost-Sharing
Agreement
FM . . . . . . . . . . . . . . fineness modulus
FRC . . . . . . . . . . . . . . fiber-reinforced concrete
GDM . . . . . . . . . . . . . generic design memorandum
GGBF . . . . . . . . . . . . ground granulated blast-furnace
GQA . . . . . . . . . . . . . government quality assurance
HRWRA . . . . . . . . . . . high-range water-reducing
admixture
HQUSACE . . . . . . . . . Headquarters, US Army Corps
of Engineers
MSA . . . . . . . . . . . . . maximum size aggregate
NMSA . . . . . . . . . . . . nominal maximum size
aggregate
NISA . . . . . . . . . . . . . nonlinear, incremental structural
analysis
PA . . . . . . . . . . . . . . . preplaced-aggregate concrete
PED . . . . . . . . . . . . . . preconstruction engineering
and design
PMP . . . . . . . . . . . . . . project management plan
P&S . . . . . . . . . . . . . . plans and specifications
SSD . . . . . . . . . . . . . . saturated-surface dry condition
w/c . . . . . . . . . . . . . . water-cement ratio
WES . . . . . . . . . . . . . Waterways Experiment Station
WRA . . . . . . . . . . . . . water-reducing admixture
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113. EM 1110-2-2000
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Appendix C
Concrete Materials Design Memorandum
C-1. Concrete Materials Investigation
The scope of the investigation will vary depending on the
quantity, criticality of the exposure condition, and the type
of structure. Critical exposure condition is defined as an
exposure condition which is deleterious to concrete such as
freezing and thawing, sulfate exposure, or acid attack. For
a small (less than 5,000 yd3
of concrete), nonhydraulic
structure exposed to a noncritical environment, investigation
will generally be limited to determining that a commercial
ready-mix plant is within acceptable haul distance. Exam-
ples of such structures include sidewalks, fireplaces, boat
ramps, and picnic table bases in a recreation area or culvert
headwalls on an access road. For a small nonhydraulic
structure which will be subjected to critical exposure
conditions, additional investigations addressing the measures
to be specified to mitigate the potential concrete deteriora-
tion should be included in the DM. Regardless of the
criticality of the exposure condition, if the structure contains
5,000 yd3
or more of concrete, a more detailed investigation
will normally be required. A more rigorous and detailed
investigation will also be required for hydraulic structures
such as locks, dams, intake structures, powerhouses, major
pumping stations, urban floodwalls, concrete-lined channels,
tunnel linings, and appurtenant structures of earth-fill dams.
A separate DM is required for lock or dam.
C-2. Concrete Materials Design Memorandum
The following typical information should be covered in
concrete materials design memoranda for various types of
structures and exposure conditions.
a. Small nonhydraulic structure (less than
5,000 yd3
of concrete) subjected to noncritical exposure
condition.
(1) Concrete quantity.
(2) Environmental and functional conditions to
which concrete will be subjected.
(3) Source of concrete (available commercial
ready-mix plants).
(4) Availability of aggregate of the quality and
grading which is to be specified.
(5) Determination of strength or w/c requirements.
b. Small nonhydraulic structure (less than
5,000 yd3
of concrete) subjected to critical exposure
condition.
(1) Concrete quantity.
(2) Description of critical environmental and/or
functional conditions to which concrete will be subjected.
(3) Specifications requirements to be used to
obtain satisfactory durability, including thermal consider-
ations of placing temperature and insulation.
(4) Availability of concrete meeting the specifica-
tions from commercial ready-mix plants in the project area.
(5) Availability of aggregate of the quality and
grading which is to be specified.
(6) Determination of strength or w/c requirements.
c. Hydraulic structures other than lock or dam or
large nonhydraulic structure (5,000 yd3
or more of concrete)
regardless of the criticality of the exposure condition.
(1) Structures in this category include:
(a) Powerhouse superstructures.
(b) Bridges.
(c) Fish hatchery complexes.
(d) Visitor centers.
(e) Water or vehicular tunnel linings.
(f) Major pumping stations.
(g) Intake structures.
(h) Urban floodwalls.
(2) Brief description and location of project.
(3) Concrete investigation.
(a) Concrete quantity.
(b) Climatic and functional conditions to which
concrete will be subject (frost action, sulfate attack, acid
water, etc.).
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114. EM 1110-2-2000
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(c) Concrete qualities to be required.
(d) Typical sectional views of various portions of
the structures showing classes of concrete.
(4) Portland cement investigation.
(a) Special requirements to be specified for
cementitious materials (low alkali, heat of hydration, false
set, C3A limitations, etc.).
(b) Availability of these cementitious materials.
(c) Types of cementitious material to be specified
with justification.
(d) Testing requirements.
(e) Cost data.
(5) Pozzolan and other cementitious materials
investigation.
(a) Types investigated for use.
(b) Availability.
(c) Cost data.
(6) Aggregate investigation.
(a) Description of aggregate sources investigated
including photographs of working faces of operating
quarries.
(b) Cost estimates.
• Cost at source.
• Distance to project.
• Available mode of transportation.
• Transportation cost.
• How a source’s use affects the cost of cementitio-
us material due to aggregate reactivity, water requirement,
strength characteristics, etc.
(c) Documentation of aggregate quality.
• Reference
• Reference to TM 6-370 (USAEWES 1953)*,
including volume numbers, area, latitude, longitude, and
index number.
• If satisfactory TM 6-370 data are not available,
local aggregate sources should be evaluated as outlined in
paragraph 2-3.
(d) Service records.
(e) Map showing location of project and deposits.
(f) Volume of concrete of each maximum size
aggregate (MSA).
(g) Recommendations as to which sources should
be listed in the specifications.
(h) Recommendations for required aggregate quality
tests and test limits and discussion of how test limits were
set.
(7) Construction plant investigation.
(a) Onsite batch plant requirements, type and
capacity.
(b) Mixer requirements, type.
(c) Commercial ready-mix plant availability,
capacity and plant type.
(d) Special requirements (time of delivery, tempera-
ture control, maximum lift thickness, insulation, curing
methods, including requirements for shielding concrete from
the direct rays of the sun on areas cured with clear curing
compound).
(e) Conveying requirements.
d. Lock or dam or both (separate DM).
(1) Description and location of project.
(2) Concrete investigations.
(a) Approximate quantities of concrete in various
structures or parts of structures by types or classes.
* References cited in this appendix are given in Appendix
A of this EM.
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115. EM 1110-2-2000
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(b) Anticipated number of separate contracts with
concrete quantities included in each contract.
(c) Climatic and functional conditions to which
concrete will be subjected.
(d) Concrete qualities to be required, include
anticipated instructions to be furnished the government
resident engineer (see paragraph 6-2).
(e) Sectional views of various portions of the
structures showing classes of concrete.
(3) Portland cement investigations.
(a) Types of portland cement to be specified,
including special requirements with justification.
(b) Availability of these cementitious materials.
(c) Testing requirements.
(d) Results of laboratory studies to determine
necessary cementitious contents to obtain desired concrete
qualities.
(e) Map showing location of project and sources.
(4) Pozzolan and other cementitious materials
investigation.
(a) Types of pozzolan and other cementitious
materials investigated.
(b) Availability of pozzolans and other cementitious
materials.
(c) Map showing location of sources and location
of project.
(d) Cost data.
(e) Anticipated quantity of pozzolan and other
cementitious materials to be used per cubic yard of concrete
for various classes of concrete (include test data).
(f) Type(s) of pozzolan and other cementitious
materials to be specified or allowed.
(5) Aggregate investigation.
(a) Summary of aggregate investigation conducted.
(b) Description of each source investigated includ-
ing unsatisfactory sources.
(c) Aggregate processing requirements.
(d) Map showing location of project and sources.
(e) Drawing showing locations and logs of cores or
test pits.
(f) Photographs of cores or typical material from
sand and gravel deposits.
(g) Photographs of working faces in existing
quarries.
(h) Cost estimates.
• Cost at source.
• Distance to project.
• Available transportation.
• Transportation cost.
• Cost of special processing.
(i) Documentation of aggregate quality.
• Reference to TM 6-370, including volume
numbers, area, latitude, longitude, and index number.
• If satisfactory TM 6-370 data are not available,
local aggregate sources should be evaluated as outlined in
paragraph 2-3 of the text.
(j) Discussion of test results.
(k) Service records including photographs where
available.
(l) Test quarry-test pit investigations. This may
require a separate DM.
(m) Recommendations as to which sources should
be listed in the specifications.
(n) Recommendations for required aggregate
gradings, aggregate quality tests and test limits, and discus-
sion of how test limits were set.
(6) Construction plant investigation.
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116. EM 1110-2-2000
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(a) Plant requirement, type, and capacity.
(b) Mixer requirements, type, and expected capacity
and quantity.
(c) Anticipated area at project site to be reserved
for concrete production.
(7) Conveying equipment.
(a) Bucket size.
(b) Time of delivery.
(c) Conveyor belts, pumps, etc.
(8) Thermal studies. The discussion of the consid-
erations related to the steps necessary to minimize the
effects of the heat of hydration in a massive structure may
be of such length as to justify a separate DM or a
separate chapter or appendix in the concrete materials DM.
The following items should be discussed:
(a) Concrete properties used as input to the
nonlinear, incremental structural analysis (NISA).
(b) Results of the NISA.
(c) Insulation requirements including R-value and
duration.
(d) Special curing requirements.
(e) Lift thickness.
(f) Minimum time between lifts.
(g) Form stripping time.
(h) Maximum placing temperature.
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Appendix D
Alkali-Silica Aggregate
Reactions
D-1. Alkali-Silica Aggregate Reactions
a. General. The use of certain aggregates in
concrete may result in a chemical process in which particu-
lar constituents of the aggregates react with alkali hydrox-
ides dissolved in concrete pore solutions. These alkali
hydroxides are derived mostly from the sodium and potassi-
um in portland cement and other cementitious materials, but
occasionally alkalies may be introduced into concrete from
external sources or may be released slowly from certain
alkali-bearing rock components within the aggregate. While
many aggregates may react in concrete, distress in structures
is observed only when significant amounts of expansive
reaction products are formed, and they take up water and
expand. The reaction products concerned are hydrous gels
whose chemical composition always includes silica, alkalies,
and at least a little calcium. The silica component is always
derived from the reactive aggregate, which is usually an
amorphous or metastable crystalline form of silica; some-
times it is a more complex assemblage of fine-grained
silicate components. Some authorities distinguish between
"alkali-silica" and "alkali-silicate" reactions, but the distinc-
tion is not clear cut. By itself, the formation of alkali-silica
reaction product creates little distress; the damage in
concrete is associated with subsequent expansion and
cracking that occurs when the reaction product gel absorbs
water and swells. Keeping affected concrete dry often
prevents or at least mitigates the deleterious response.
Alkali-aggregate reactions were first observed in California
in the 1940’s but have subsequently been recognized in
many countries. In the United States, alkali-silica reactive
aggregates are more common in western and southwestern
states; in certain parts of the Southeast, including especially
Alabama, South Carolina, and Georgia; and in some of the
Great Plains states.
b. Nature of the reaction. Field evidence for the
occurrence of alkali-silica reaction in a given concrete in-
cludes expansion and development of polygonal or map
cracking as a characteristic feature, especially when
accompanied by gel deposits exuding from the cracks.
However, a number of other causes of distress may show
superficially similar features, and a petrographic
examination of the affected concrete is generally necessary
to confirm that alkali-silica reaction is actually taking place.
Generally speaking, the higher the alkali content of the
cement used, the higher the resulting alkali-hydroxide
concentration and pH and the greater the potential for alkali-
silica attack. The specific reacting agent is the hydroxide
ion itself. The hydroxide ions break Si-O-Si bonds in the
reactive silica or siliceous aggregate components, thus
breaking up their cross-linked structure and isolating and
dissolving individual silica tetrahedral units. In the absence
of calcium, such reaction merely produces dissolved silica.
However, in the presence of the solid calcium hydroxide
always found in hydrated cement, an alkali-silica gel
containing some calcium is formed. In the past, it has been
suggested that only gels of minimum calcium content were
expansive and gels of higher calcium content were limited
swelling gels not capable of causing distress, but some
workers now suggest that this seems not to be the case.
One of the common petrographic features of alkali-silica
reaction is the occurrence of a zone immediately
surrounding the reacting aggregate particle in which the
cement paste is partially or wholly depleted of calcium
hydroxide, the latter having been incorporated into the gel.
The actual distress in concrete is associated not with
formation of the gel product but with subsequent expansion
taking place when gel absorbs water (or solution) and
swells. The swelling pressure generated may be of the
order of 7 MPa (1,000 psi), sufficient to crack the
surrounding paste. If many aggregate grains have reacted
to form gel and if sufficient water is available, the combined
effect results in macroscopic swelling and eventually a
visible crack pattern develops. In some concrete structures
that are geometrically sensitive, the irregular expansion itself
may be highly damaging to proper functioning, even if
visible cracks or other evidences of concrete deterioration
are hardly developed. Reactions with strained quartz and
with reactive silicate aggregates generally are slower than
other alkali-silica reactions, but slow expansion may
continue for many years. Such reactions may produce
comparatively little reaction gel and are particularly difficult
to identify without petrographic examination. Among the
unusual features of the alkali-silica reaction is the existence
of a so-called "pessimum effect." If mortars or concretes
are made using varying proportions of reactive and inert
aggregate, the expansion may be greatest for a mixture with
a comparatively small proportion of the reactive component.
The proportion giving rise to the greatest expansion is the
pessimum proportion. This proportion is particularly low
with opal. With most other common types of reactive
aggregate, the pessimum proportion is usually higher, and in
some cases, it is 100 percent, i.e., the pessimum effect does
not occur.
D-2. Criteria for Recognition of Potentially
Deleterious Constituents in Aggregate
A number of siliceous components of aggregates may be
potentially reactive. Reactive aggregate components may be
found in igneous, sedimentary, or metamorphic rocks of
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118. EM 1110-2-2000
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various textures and ages. Among the more commonly
encountered reactive aggregate components are:
a. Reactive substances.
(1) Opal. Opal is a variety of amorphous silica with
a porous internal structure which contains water. Opal may
occur in cherts, volcanic rocks, shales, sandstones, and
carbonate rocks; frequently, it may occur in segregated
forms in cavity fillings, crack linings, or as cementing
material in concretions. Opal is the most reactive of the
various reactive aggregate components ordinarily encoun-
tered and may cause damage in concrete when as little as a
fraction of a percent is present in the aggregate.
(2) Chalcedony. Chalcedony is a siliceous component
of some cherts; microscopically it is distinguished by
radiating sheaf-like or fibrous structures embedded in a
groundmass from which they cannot be separated. Chalce-
donic material is largely very fine quartz, but amorphous
silica may be present as well.
(3) Volcanic glass. Particles of volcanic glass or
sometimes devitrified volcanic glass in aggregates may be
reactive, depending on composition. Acid glasses (those of
silica content above 65 percent) and intermediate glasses (of
silica contents between 55 and 65 percent) are commonly
reactive; more basic glasses (silica content below 55 perce-
nt) are less so. Reactive glasses may be identified by
refractive indices below 1.57. The presence of water in
volcanic glasses seems to be associated with reactivity.
(4) Tridymite and cristobalite. These are crystalline
forms of silica that are metastable at ordinary temperatures
but that may be found in various igneous rocks, especially
andesites and rhyolites.
b. Other potentially reactive substances. In addition
to these substances just listed, the following may also be
reactive:
(1) Quartz. Well crystallized quartz may be reactive
and may give rise to problems in concrete if the crystals are
strained and finely crushed material produced as in fault
zones (mylonite) by virtue of previous geological activity.
Strained quartz can be detected petrographically by measure-
ment of the undulatory extinction angle. Rocks such as
granites and sandstones may thus be suspect if the forma-
tions from which they are derived have a history of exten-
sive metamorphic activity.
(2) Silicates. Various sedimentary or metamorphic
rock types containing clays or micas have been observed to
be reactive. Such rock types include graywackes, argillites,
phyllites, siltstones, etc. There is considerable dispute as to
whether the reactive component is finely divided quartz or
amorphous silica within the rock or whether the reaction
involves the clay mineral or mica components. Alkali
reactions with such rock types tend to be unusually slow
and may escape detection by the normal screening tests for
reactive aggregate. If aggregate to be used contains
significant contents of such rock types, low-alkali cement
should be used where available. If not available or if it is
available only at greatly increased cost, additional studies
may be required and HQUSACE should be notified (Atten-
tion: CECW-EG).
(3) Sandgravel. "Sandgravel" aggregates in parts of
Kansas, Nebraska, and Wyoming, especially those from the
Platte, Republican, and Laramie Rivers, have been involved
in the deterioration of concrete. Aggregates from these
areas should be viewed with suspicion unless an acceptable
service record has been compiled or no reactive constituents
are found on petrographic examination.
(4) Disseminated silica in limestones. A number of
instances of alkali silica reactivity leading to serious distress
have been observed with limestone aggregate that contains
small amounts of dispersed silica, often skeletal remains of
small organisms. The fact that limestone aggregates may
not be of the characteristic dolomite composition and
impurity content that results in alkali-carbonate reaction
does not preclude the possibility of alkali-silica reaction if
disseminated reactive silica exists in the material.
D-3. Methods of Determining the
Potential for Reactivity
a. Standard methods.
(1) American Society for Testing and Materials
(ASTM) C 227 (CRD-C 123) - "Potential Alkali Reactivity
of Cement-Aggregate Combinations (Mortar-Bar Method)."*
In this method the length change of mortar bars prepared
with the aggregate in question (prepared to a specified
particle size distribution) and either high-alkali or the
specified job cement is measured over a 1-year period.
* Test methods cited in this manner are from the Annual
Book of ASTM Standards (ASTM 1992) and from the
Handbook of Concrete and Cement (U.S. Army Engineer
Waterways Experiment Station (USAEWES) 1949), respec-
tively. References cited in this appendix are given in
Appendix A of this EM.
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119. EM 1110-2-2000
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(2) ASTM C 289 (CRD-C 128) - "Potential Reactivi-
ty of Aggregates (Chemical Method)." In this so-called
"quick chemical test," finely crushed aggregate is immersed
in concentrated sodium hydroxide and heated under pressure
for 24 hours. The reaction is monitored by subsequent
determination of the amount of dissolved silica and the
degree of reduction in the alkalinity of the solution. This
test gives an indication of possible reactivity but is not
sufficiently definitive to be used alone without additional
testing.
(3) ASTM C 295 (CRD-C 127) - "Petrographic
Examination of Aggregates for Concrete." This is the
procedure for petrographic examination of aggregates,
including the determination of whether potentially deleteri-
ous components are present. The services of a qualified
petrographer are required.
(4) A test method involving measurement of length
change of concrete prisms rather than mortar bars has
recently been adopted by the Canadian Standards Associa-
tion (CSA) (CSA A23.2-14A 1986). It is intended to
overcome criticism of other tests that they do not involve
concrete specimens.
b. Nonstandard methods of determining the potential
for alkali reactivity.
(1) General. A number of nonstandard methods have
been developed to determine potential reactivity of aggre-
gates. Noteworthy among these is the osmotic method
described by Stark, high-temperature accelerated test
described by Oberholster and Davies (1986), and two very
recent rapid tests: a staining procedure developed by Poole,
McLachlan, and Ellis (1988) and a fluorescent method
reported by Natesaiyer and Hover. While none of these
procedures has yet replaced any of the standard methods of
test for reactive aggregates, they may constitute useful
supplementary tests that can be carried out relatively
quickly. Most of them require some special apparatus.
(2) Osmotic method. In the osmotic method,
powdered aggregate is immersed in sodium hydroxide and
separated by a cement paste membrane from a reservoir of
sodium hydroxide of the same concentration. The
osmotically induced flow of the fluid from the reservoir to
the solution containing the aggregate is monitored, and if it
exceeds a specified amount in several weeks, the aggregate
is considered reactive.
(3) Accelerated test. In the high-temperature
accelerated test, mortar prisms made according to the
procedure of ASTM C 227 (CRD-C 123) are immersed in
a one-normal sodium hydroxide solution at 80 °C (176 °F)
for 12 days with measurements of expansion made daily.
An expansion of 0.11 percent or greater over this period is
taken as indicating that the aggregate is deleteriously
reactive.
(4) Staining test. In the staining procedure, the
potentially reactive rock is reacted with a special alkali
solution so that the gel formed gives rise to a blue-colored
complex; the intensity of the color is measured and related
to the reactivity of the rock.
(5) Fluorescence test. In the fluorescence method,
uranyl acetate solution is applied to the concrete; if gel has
formed, uranyl ions are quickly exchanged for alkali ions.
The presence of such uranyl-bearing gel is easily observed
by examination under ultraviolet light.
D-4. Reliability of Available Test Methods
a. General. Despite continuing research and
improvements, none of the standard methods can be relied
on independently or collectively to provide an unquestion-
ably definitive answer, especially to the question of whether
seriously deleterious reaction should be expected if small
amounts of moderately reactive components are discovered.
b. Petrographic examination. The results of petro-
graphic examination by an experienced petrographer should
provide an indication of the presence of any potentially
reactive components in the aggregate. The mortar-bar test
should provide an indication of whether any reactions taking
place will be extensive enough to induce unacceptable levels
of expansion. Thus, combining the results of petrographic
examination with mortar-bar expansion test results is
considered to be the most reliable way to predict possible
excessive expansion using the standard test procedures.
However, contradictory indications will sometimes be
provided by the results of the two methods, and both
methods entail certain uncertainties. Petrographic examina-
tion requires interpretation, and small amounts of certain
important components, especially opal, can readily be
missed. Mortar-bar tests require at least 6 months and may
not even then detect certain slow forms of reactivity.
Furthermore, the reproducibility of the mortar-bar test is not
high.
c. Quick chemical test. The quick chemical test is
generally considered to be of limited reliability; its major
advantage is that it can be accomplished in little more than
a day. Spurious results may be obtained in the presence of
carbonate rock components.
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120. EM 1110-2-2000
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d. Test samples. All of these methods require that
the small volume of aggregate sample examined be truly
representative of the very large and often inhomogeneous
deposit being sampled. This often poses an impossible
condition, even when standard methods of aggregate
sampling (e.g. those specified in ASTM D 75 (CRD-C 155)
amd ASTM D 3665) are employed.
e. CSA concrete test. The CSA concrete test was
designed to provide a rapid indication of reactivity particu-
larly with a fine-grained silicate rock. Unfortunately, since
no minimum expansion limit is prescribed, interpretation of
the results are difficult.
f. Osmotic test. The osmotic test has been used for
a number of years by the Portland Cement Association and
its Construction Technology Laboratories Division and
appears to give promising results. Similarly, the accelerated
high temperature test has been used for a few years by the
National Building Research Institute in South Africa, and it
too appears promising for future adoption. The staining and
fluorescent analysis procedures are so new that their
reliability has not been assessed.
D-5. Criteria for Evaluating
Potential Reactivity
a. General. The fine and coarse aggregates suggest-
ed for use in a given concrete mixture should be evaluated
separately for potential reactivity, regardless of whether or
not they come from the same source.
b. Petrographic analysis results. A fine or coarse
aggregate will be classified as "potentially deleteriously
reactive," i.e. capable of causing damage to concrete made
with high-alkali cement, if the petrographic examination
reveals any of the following:
(1) Presence of any opal.
(2) More than 5 percent of particles of chert in which
any chalcedony is detected.
(3) More than 3 percent of particles of glassy igneous
rocks in which any acid or intermediate glass is detected.
(4) More than 1 percent of particles in which any
tridymite or cristobalite is detected.
(5) More than 20 percent of particles containing
strained quartz in an aggregate in which the measured
average extinction angle is at least 15 degrees.
(6) More than 15 percent of particles consisting of
graywacke, argillite, phyllite, or siltstone containing any
very finely divided quartz or chalcedony.
c. Mortar-bar results. A fine or coarse aggregate
will be classified as "potentially deleteriously reactive" if the
expansion measured in tests with cement containing not less
than 1.0 percent alkalies calculated as Na2O is more than
0.05 percent at 6 months or 0.10 percent at 1 year. Addi-
tionally, the following interpretations should be made:
(1) Measured expansions greater than 0.10 percent at
any age are indications that the aggregate should be regard-
ed
as potentially deleteriously reactive.
(2) Measured expansions greater than 0.05 percent at
6 months but less than 0.10 percent at 1 year usually
indicate that the aggregate is not deleteriously reactive, but
in borderline cases, the slope and trend of the length change
versus time curve should be examined for assistance in
interpretation.
(3) If the aggregate contains strained and very finely
divided quartz, but either the content of such particles or the
degree of strain is such that the criteria mentioned previous-
ly for strained quartz aggregate are not exceeded, additional
special mortar-bar tests should be carried out. In these tests
the mortar bars are made using a nonreactive fine aggregate,
but five particles of a size between 12.5 and 19.0 mm (1/2
to 3/4 in.), consisting entirely or mostly of the strained
quartz, are inserted into each bar. The bars are stored under
conditions of 100 percent RH and a temperature of 60 ° ±
5 °C (140 ° ± 10 °F). The aggregate so tested will be
considered potentially deleteriously reactive if expansion at
6 months exceeds 0.025 percent or expansion at 1 year
exceeds 0.04 percent. These special criteria are invoked
because of the observed slow rate of expansion of concrete
containing reactive strained and very finely divided quartz.
d. Quick-chemical test criteria. A fine or coarse
aggregate will be classified potentially deleteriously reactive
or deleteriously reactive if the data point plotted for it falls
to the right of the line on the standard graph accompanying
the description of the test method.
e. Service record. A fine or coarse aggregate will be
classified as potentially deleteriously reactive when service
records establish that excessive expansion due to alkali-silica
reaction has occurred in a structure in which the aggregate
has been used. Where service records indicate deleterious
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121. EM 1110-2-2000
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reactivity, the aggregate should be so classed, regardless of
laboratory test results. As previously indicated, the
laboratory test methods cannot be absolutely relied on,
individually or collectively, to provide an unquestionably
positive indication of potentially excessive expansion.
Every effort should be made to obtain prior performance
records, especially where cements of high-alkali contents
have been used, and especially if exposure conditions have
been similar to those predicted for the proposed work. It
should be noted that some reactions occur slowly and take
years to become evident. Care should be taken on younger
structures.
f. Blended aggregates. If either the coarse or fine
aggregates for a project will be blended from aggregate
derived from two or more sources, the combined coarse or
fine aggregate, in the proportion intended for use, will be
evaluated for potential reactivity. In the petrographic
examination, the estimated amounts of potentially
deleterious constituents present will be calculated by the
method of weighted averages, using the proposed grading of
the blended coarse or fine aggregate. For the mortar-bar
test, where fine aggregate is to be blended from two or
more sources, each sieve fraction used in the test shall be in
proportion to that sieve fraction in the proposed blended fine
aggregate. For blended coarse aggregates, the crushed
material from which the test mortars are prepared shall
include all of the rock types occurring in the combined
coarse aggregate, in the percentages of each size group
anticipated for the combined grading of the project
aggregate. Similar procedures should be used to select
aggregate to be powdered for sample material for use in the
quick-chemical test.
g. Application of standard test criteria. It is
preferred that each fine or coarse aggregate be evaluated
based on a combination of service record, petrographic
examination, mortar-bar, and quick-chemical test results. If
the indications disagree, aggregates are to be considered
potentially deleteriously reactive if so indicated by the
following combinations of tests:
(1) Service records and mortar-bar test results.
(2) Service records and petrographic examination.
(3) Mortar-bar test results and quick-chemical test
results.
(4) Petrographic examination and quick-chemical test
results.
(5) If in the absence of mortar-bar test results,
petrographic examination indicates that the aggregate is
potentially deleteriously reactive, but this is not confirmed
by either service record or results of the quick-chemical test,
the aggregate should not be used until the results of mortar-
bar testing can be obtained.
D-6. Control of Alkali-Silica Aggregate Reactions
Aggregates considered potentially deleteriously reactive
should not be used in concrete that will be exposed to
moisture in service. If such use is unavoidable, suitable
precautions must be taken to minimize the probability of
harmful internal expansion and cracking. Such precautions
include the following:
a. Use of low-alkali cements. If it appears likely that
low-alkali cement, i.e., cement meeting the optional
requirement for low-alkali content of ASTM C 150 (CRD-C
201) will be available at little or no increase in cost, this
optional requirement should be invoked and such cement
used. However, experience has indicated that such use does
not provide a complete guarantee that no distress will be
experienced, especially if (a) the structure is a slab on grade
exposed to relatively high temperature and low relative
humidity conditions so that the alkalies become concentrated
in the region near the surface, (b) alkali from external
sources can be expected to penetrate the concrete, or
(c) alkalies are released internally from certain aggregate
components as a result of reaction with cement hydration
products.
b. Use of slag or pozzolans. If low-alkali cement is
not available or available only at excessive cost, the use of
a GGBF slag or a mineral admixture such as a pozzolan (fly
ash, silica fume, or natural pozzolan) (or a blended cement
containing such a component) is indicated. These
components effectively absorb hydroxide ions and alkali
ions from the concrete pore solutions, thus reducing the
driving force for the deleterious alkali-silica chemical
reaction with aggregate. While blended portland blast-
furnace slag cements are not widely available, separately
batched GGBF slag may be used to provide a GGBF slag-
portland-cement concrete highly resistant to alkali-silica
attack. Silica fume added in much smaller percentages than
slag has also been highly effective, although the cost
involved may be high. Some slags, fly ashes, and other
pozzolans provide effective protection against the alkali-
silica reaction, some do not. Fly ashes and natural
pozzolans must meet the requirements of ASTM C 618,
Table 2A, Supplementary Optional Physical Requirements,
Reactivity with Cement Alkalies, to be considered effective.
Slag must meet the requirements of ASTM C 989,
Appendix X3, to be considered effective. These
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122. EM 1110-2-2000
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specifications give criteria for determining the effectiveness
of the material. Silica fume should be considered a
pozzolan for this discussion and should be evaluated per
ASTM C 618.
c. Determination of the minimum amount of pozzolan
or slag to use to control alkali-silica reaction.
(1) The proposed material should be given a
preliminary characterization by a combination of physical,
chemical, and petrographic methods to assure that it is a
reasonable candidate material and that it meets the
applicable specifications.
(2) Prepare four mortar mixtures according to
ASTM C 441 (CRD-C 257). Use the proposed cement or
high-alkali cement and Pyrex glass as the aggregate on the
assumption that if the candidate pozzolan (fly ash, silica
fume, or natural pozzolan) or slag will control this
combination, it will control the actual job materials. Pyrex
glass is preferred since its pessimum amount is 100 percent.
This avoids the need to conduct tests to determine the
pessimum amount of reactive material in the actual
aggregate and possible fluctuations in test results due to
nonuniformity of the aggregate. A control mixture without
pozzolan or slag should be made.
(3) Test the bars from these mixtures by
ASTM C 441 (CRD-C 257) for a minimum of 14 days,
longer if possible.
(4) Evaluate the expansion data to determine the
amount of slag or pozzolan needed to keep expansion from
exceeding the criteria given in the appropriate specifications.
(5) This is the amount to use in the concrete. If may
be necessary to make slight modifications to the intended
concrete mixture to assure desired workability or strength
gain or other needed properties.
(6) Once a material and its amount to use has been
selected, the continued suitability of this material during the
duration of construction should be periodically monitored by
selected physical or chemical or petrographic methods or a
combination of these. For example, one might use fineness,
silica content, or relative amount of glass. Similar
monitoring should be used for the cement. The frequency
of testing and parameters to be used must be determined and
documented in the concrete materials design memorandum.
(7) It is desirable to approximate the actual
environmental conditions during the laboratory testing. If
there is a significant source of alkali from the environment,
it may affect the control provided by the pozzolan or slag
and could necessitate the use of nonreactive aggregate.
d. Decreasing the availability of water. Concretes
batched at low w/c have only a limited supply of internal
water needed to cause the alkali-silica reaction product gel
to swell, and the permeability of such concretes to outside
water is also reduced. Thus, the deleterious consequences
of the alkali-silica reaction may be slowed down
significantly. Experience has also indicated that when
concrete dries sufficiently that the relative humidity in the
pores of the concrete falls below and remains below 80
percent, no adverse expansion occurs. However, the
chemical reaction is not necessarily precluded, and
subsequent rewetting may produce rapid and serious
expansions.
e. The sandgravel problem. So-called sandgravel
aggregates derived from river-transported deposits along the
Platte, Republican, Laramie, and several other rivers in the
Great Plains states (notably Kansas, Nebraska, Colorado,
Wyoming, and to a lesser extent Iowa and Missouri) cause
characteristic problems in concrete. In part, these
difficulties are due to the poor grading of these materials,
but alkali-aggregate reactivity is associated with glassy
volcanic components in the western part of the region and
opal combined with lesser amounts of volcanic glass to the
east. Neither the use of low-alkali cements nor the use of
pozzolans have completely succeeded in controlling the
problem. Accordingly, aggregates from these sources
should be avoided if economically feasible to do so. If this
is not feasible, replacement of at least 45 percent of the
aggregate with crushed limestone appears to be an effective
remedy when combined with the use of low-alkali cement.
f. Decreasing the amount of reactive aggregate. It
may be economical to use some proportion of local reactive
aggregate with the rest being more expensive imported
nonreactive aggregate, rather than use all imported
aggregates. The proportion of reactive aggregates that can
safely be used must be carefully investigated.
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123. EM 1110-2-2000
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Appendix E
Alkali-Carbonate Rock Reactions
E-1. General Statement.
The results of studies that have been reported indicate that
four types of alkali-carbonate rock reaction may be
recognized in concrete. A thorough review of research
through 1964 is contained in paragraph E-4 of this manual
(Highway Research Board 1964).* It is possible that future
work will show that some of these are merely different
manifestations of the same reaction, shown by different
rocks under a variety of circumstances. The four types of
reactions are discussed in the following subparagraphs:
a. Reactions involving nondolomitic carbonate rocks.
Some rocks which contain little or no dolomite may be
reactive (Mather et al. 1963; Buck 1965). The reaction is
characterized by reaction rims which are visible along the
borders of cross sections of aggregate particles. Etching
these cross-sectional surfaces with dilute hydrochloric acid
reveals that the rims are "negative" rims, i.e. the reaction
rim zone dissolves more rapidly than the interior of the
particle. The evidence to date indicates that the reaction is
not harmful to concrete and may even be beneficial.
b. Reactions involving dolomite or highly dolomitic
carbonate rocks. The reaction of dolomite or highly
dolomitic aggregate particles in concrete has been reported
(Tynes et al. 1966). The reaction was characterized by
visible reaction rims on cross sections of the aggregate
particles. When these cross-sectional areas of aggregate
particles were etched with acid, the rimmed area dissolved
at the same rate as the nonrimmed area. No evidence was
reported that this reaction was damaging to concrete.
c. Reactions involving impure dolomitic rocks. The
rocks of this group have a characteristic texture and
composition. The texture is such that larger crystals of
dolomite are scattered in and surrounded by a fine-grained
matrix of calcite and clay. The rock consists of substantial
amounts of dolomite and calcite in the carbonate portion,
with significant amounts of acid-insoluble residue consisting
largely of clay. Two reactions have been reported with
rocks of this sort, as follows:
(1) Dedolomitization reaction. This reaction is
believed to have produced harmful expansion of concrete
(Hadley 1961). Magnesium hydroxide, brucite (Mg (OH)2),
* References cited in this appendix are given in Appendix A
of this EM.
is formed by this reaction; its presence in concrete which
has expanded and which contains carbonate aggregate of the
indicated texture and composition is strong evidence that
this reaction has taken place.
(2) Rim-silicification reaction. This reaction is not
definitely known to be damaging to concrete, although there
are some data which suggest that a retardation in the rate of
strength development in concrete is associated with its
occurrence. The reaction is characterized by enrichment of
silica in the borders of reacted particles (Bisque and Lemish
1958). This is seen as a positive or raised border at the
edge of cross sections of reacted particles after they have
been etched in dilute hydrochloric acid. Reaction rims may
be visible before the concrete surfaces are etched.
Fortunately, carbonate rocks that contain dolomite, calcite,
and insoluble material in the proportions that cause either
the dedolomitization or rim-silicification reactions are
relatively rare in nature as major constituents of the whole
product of an aggregate source.
E-2. Criteria for Recognition of Potentially
Harmfully Reactive Carbonate Rocks
These criteria serve to indicate those dolomitic carbonate
rocks capable of producing the dedolomitization or rim-
silicification reaction. Since the reactions generated by
some highly dolomitic or by some nondolomitic carbonate
rocks are not known to be harmful to concrete, no attempt
is made to provide guides for recognition of these rocks at
this time.
a. Petrographic examination. When petrographic
examinations are made according to ASTM C 295 (CRD-C
127) of quarried carbonate rock or of natural gravels
containing carbonate-rock particles, adequate data
concerning texture, calcite-dolomite ratio, the amount and
nature of the acid-insoluble residue, or some combination of
these parameters will be obtained to recognize potentially
reactive rock. Rocks associated with observed expansive
dedolomitization have been characterized by fine-grain size
(generally 50 micrometres or less) with the dolomite largely
present as small, nearly euhedral crystals generally scattered
in a finer-grained matrix in which the calcite is
disseminated. The tendency to expansion, other things
being equal, appears to increase with increasing clay content
from about 5 to 25 percent by weight of the rock, and also
appears to increase as the calcite-dolomite ratio of the
carbonate portion approaches 1:1.
b. Testing. Samples of rock recognized as potentially
reactive by petrographic examination will be tested for
length change during storage in alkali solution in accordance
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124. EM 1110-2-2000
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with ASTM C 586 (CRD-C 146). Rock characterized by
expansion of 0.1 percent or more by or during 84 days of
test by ASTM C 586 should be classified as potential
reactive.
c. Service record. If adequate reliable data are
available to demonstrate that concrete structures containing
the same aggregate have exhibited deleterious reactions, the
aggregate should be classified as potentially reactive on the
basis of its service record.
E-3. Control of Alkali-Carbonate Reaction
The application of engineering judgment will be required in
making the final decision as to which rocks are to be
classified as innocuous and which are to be classified as
potentially reactive. Once a rock has been classified as
potentially reactive, the action to be taken should be as
indicated in the following subparagraphs.
a. Reactive aggregate. Avoid use of aggregate of
rock classified as potentially reactive by appropriate
procedures such as selective quarrying.
b. Other control methods. If it is not feasible to
avoid the use of rock classified as potentially reactive, then
specify the use of low-alkali cement and pozzolan, the use
of the minimum aggregate size that is economically feasible,
and dilution so that the amount of potentially reactive rock
does not exceed 20 percent of the coarse or fine aggregate
or 15 percent of the total if reactive material is present in
both.
c. Aggregate source. If it is not practical to enforce
conditions in subparagraphs a or b, then the aggregate
source that contains potentially reactive rock shall not be
indicated as a source from which acceptable aggregate may
be produced.
E-2